Module 6 – Genetics, Evolution & Ecosystems Flashcards
(180 cards)
1
Q
C19) What is the meaning of mutation
A
A mutation is a change in the sequence of bases in DNA
2
Q
C19) What are the causes of Gene mutations
A
Substitution, deletion or insertion of one or more nucleotide within a gene.
If only one nucleotide is affected it is called a point mutation
3
Q
C19) What are the effects of substitution in gene mutations
A
Changes the codon on in which it occurs.
New codon codes for a different amino acid this will lead to a change in the primary structure of the protein
Degenerate nature of the genetic code may mean however that the new codon make code still for the same amino acids leading to no change in protein synthesis
4
Q
C19) What are the effects of insertion and deletion in gene mutations
A
Lead to a frameshift.
Each group of three bases correspond to one amino acid the addition or deletion of a nuclear tide moves the reading frame of the sequence of bases therefore changing every code on from the point of mutation
5
Q
C19) what are the effects of different genetic mutations on the phenotype
A
No effect – because normally functioning proteins are still synthesised
Damaging - than the phenotype is affected negatively because proteins are no longer synthesised or non-functional affecting with essential processes
Beneficial - very rare a protein is synthesise that results in a new and useful characteristic in the phenotype. For example a mutation in a protein in the cell surface membrane means that HIV cannot bind and enter the cells
6
Q
C19) what are the causes of mutations
A
Mutations can occur spontaneously during DNA replication but the rate of mutation is increased by mutagens
The loss of bases often occur spontaneously. The absence of a base can lead to the insertion of an incorrect base through complimentary base pairing during DNA replication
Free radicals are oxidising agents which affect the structures of nuclear tides and disrupt base pairing during DNA replication
Antioxidants vitamins that are known as anticarcinogens because of the ability to negate the effects of free radicals
7
Q
C19)What is a silent mutation
A
They do not change any proteins or the activities of any proteins synthesised meaning they have no effect on the phenotype.
Can occur inThe non-coding regions of DNA or code for the same amino acid because of the degenerate nature of the genetic code
May result in the change of the primary structure but do not change the overall structure or function of the protein
8
Q
C19)What is a nonsense mutation
A
Results in a code on becoming a stop codon instead of coding for an amino acid
Resulting in the shortening of the protein being synthesised resulting in non-functionality. Negative or harmful effect on the phenotype
9
Q
C19 what is a missense mutation
A
Result in the incorporation of an incorrect amino acid into the primary structure when the proteins synthesised
The result depends on the role of the amino acid in the structure and function of the protein
Conservative mutations occur when the amino acid change leads to an amino acid being coded for with similar properties of the original meaning the mutation is less serious
Non-Conservative mutation is when the new amino acid coded for has different properties to the original so more likely to have an effect on the protein structure and cause disease
10
Q
C19) what is an example of a beneficial mutation
A
The ability to digests lactose is thought to be the result of a mutation.
Majority of mammals become lactose intolerant after they cease to suckle
The ability to digest lactate is found in European population because they are more likely to farm cattle
The ability to drink milk and processed lactose as an adult prevents individuals with the mutation from starving from famines
11
Q
C19) What are the changes in chromosome structure after a chromosomal mutation
A
Caused by mutagens and normally occur during meiosis
Deletion – a section of chromosome breaks off and lost within the cell
Duplication - Sections get duplicated on a chromosome
Translocation - A section of one chromosome breaks off and joins another homologous chromosome
Inversion-a section of chromosome breakoff, is reversed and then joins back onto the chromosome
12
Q
C19) what are housekeeping Genes
A
Enzymes which are necessary for reactions like respiration are constantly needed and the genes that code for these are called housekeeping Genes
13
Q
C19) Why do bacteria regulate gene
A
They are able to respond to changes in their environment because of gene regulation
Expressing genes only when the products are needed also provides vital resources being wasted
14
Q
C19) What are the different ways in which genes are regulated
A
Transcriptional - Genes can be turned on or off
Post transcriptional - MRNA they can be modified which regulates translation and the types of proteins produced
Translational - translation can be stopped or started
Post-translational-proteins can be modified after synthesis which could change their function
15
Q
C19) what are different transcriptional controls for Gene regulation
A
Chromatin remodelling
Histone modification
Lac operon (Prokaryotes)
Role of Cyclic AMP (prokaryotes)
16
Q
C19) How does chromatin remodelling Regulate gene expression
A
DNA is a very long molecule that has to be wound around proteins called histones allowing to be packed into the nucleus of a cell this is DNA/histone complex is called chromatin.
Heterochromatin is tightly wound DNA causing chromosomes to be visible during cell division
Euchromatin is loosely wound DNA present during interphase
Gene transcription is not possible when DNA is tightly wound because RNA polymerase cannot access genes,So euchromatin can be translated
Does not occur during cell division but during interphase
Regulation insures the proteins necessary for cell division are synthesised in time and prevents the complex and energy consuming process taking place during cell division
17
Q
C19) How does histone modification Regulate gene expression
A
DNA coil around histones because they are positively charged and DNA is negatively charged
Histones can be modified to increase or decrease the degree of condensation
The addition of an acetyl group (acetylation) or phosphate group (phosphorylation) reduce the positive charge of the histone causing DNA to coil less tightly allowing for transcription
The addition of a methyl Group (methylation) making the histones more hydrophobic so they bind more tightly to each other causing DNA to coil tightly and preventing transcription of jeans
18
Q
C19) what is the meaning of Epigene
A
Used to describe the control of gene expression by modifying DNA
19
Q
C19) What is a lac operon
A
An operon is a group of genes that are under the control of the same regulatory mechanisms and are expressed at the same time
More common in prokaryotes because of the smaller and simpler structure of their genome
Also very efficient way of saving resources because if each gene products are not needed then all of the genes involved in the production are switched off
20
Q
C19) How does lac operon Regulate gene expression on a prokaryote
A
E. coli is glucose is in short supply lactose can be used as a Respiratory substrate.
The lack operon is a group of three genes,LacZ,LacY and LacA involved in the breakdown of lactose
They are structural genes as they code for three enzymes (beta Galactoside, lactose permease and transacetylase) and they are transcribed into a single long molecule of RNA
The regulatory gene (LacI) codes for a repressor protein which prevents the transcription of the structural genes in the absence of lactose
The repressor protein binds to an area called the operator which prevents RNA polymerase binding to DNA at the promoter and begin transcription this is called down regulation
When lactose is present and binds to the repressor protein causing it to change shape so it is no longer bound to the operator allowing RNA polymerase to transcribe the enzymes
21
Q
C19) how does the role of cyclic AMP regulate gene expression in a prokaryote
A
The binding of RNA polymerase results in slow rate of transcription which needs to be upregulated to produce the required quantity of enzymes to metabolise lactose
only possible when CRP is bound to cAMP
The transport of glucose into E. coli cells decrease the levels of CAMP reducing the transcription of the genes responsible for metabolise lactose, glucose becomes the primary. respiratory substrate
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Q
C19) What are the post transcriptional gene expression controls
A
RNA processing
RNA editing
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Q
C19) how does RNA processing control gene expression at the post transcriptional level
A
Transcription produces a precursor molecule called pre-mRNA this is modified forming mature mRNA before it can join to a ribosome and synthesise a protein
A cap is added to the five end and a tail is added to the three end helping to stabilise the mRNA and delay degradation in the cytoplasm. The cap binding of mRNA to ribosomes
Splicing occurs when RNA is cut at specific points. Intron (non-coding DNA) are removed and exons (coded DNA) are join together
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Q
C19) how does RNA editing Control gene expression at the post transcriptional level
A
The nucleotide sequence of some mRNA molecule can also be changed through base addition, deletion or substitution which results in the synthesis of different proteins with different functions
This increases the range of proteins that can be produced from a single mRNA molecule or gene
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C19) What are the different translational controls that control Gene expression
Degradation of mRNA-more resistant the molecule the longer it will last of the cytoplasm therefore greater quantity of protein synthesised
Binding of inhibitory proteins to mRNA prevents it binding to ribosomes and synthesising proteins
Activation of initiation factors which aid the binding of mRNA to ribosomes (the eggs of many organisms produce large amounts of mRNA which is not required until after fertilisation with the use of initiation factors)
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C19) What are the different post-translational controls that control Gene expression
Addition of non-protein groups such as carbohydrate chains, lipids and phosphate
Modifying amino acids and the formation of bonds such as disulfide bridges
Folding or shortening of proteins
Modification by cAMP
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C19)What is the meaning of morphogenesis
The regulation of the pattern of anatomy development
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C19)What are homeobox genes
A homeobox genes are a group of jeans which contain a homeobox
homeobox is section of DNA coding for a part of the protein 60 amino acid long and is highly conserved in plants ,animals and fungi
A homeodomain binds to homeobox and switches other genes on and off therefore homeobox genes are regulatory genes
pa6x when mutated causes blindness in humans. Mice and fruit flies also have this gene causing them to be blind as well.
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C19) What are Hox genes
Are a group of homeobox genes that are only present in animals.
Responsible for the correct positioning of body parts
Found in gene clusters- mammals have four clusters on different chromosomes
The order in which the gene appears along the chromosome is the order in which the effects are expressed on the organism
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C19) What are the layouts of living organisms
Body plans are usually represented as cross-section through the organism following the fundamental arrangement of tissue layers
The common feature of animals is that they are segmented (backbone of vertebrals)
The segments have multiplied over time becoming specialised for different functions
Hox genes in the head control the development of mouthparts while Hox genes in the thorax control the development of wings, limbs or ribs
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C19) what is a Diploblastic animal and triploblastic
Animals that have two primary tissue layers
Animals that have three primary tissue layers
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C19) how are humans segmented
Individual vertebra and associate structures have been developed from segments in the embryo called somites
The somites on directed by Hox genes to develop in a particular way depending on their position in the sequence
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C19) What is Radial symmetry
It is seen in Diploblastic animals like jellyfish. They have no left or right only a top on the bottom
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C19) What is bilateral symmetry
Seen in most animals means the organism has both left and right side and a head and tail
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C19) What is meant by asymmetry of an organism
Seen in sponges which have no line of symmetry
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C19) How does mitosis and apoptosis affect the body plan of an animal
Mitosis which results in cell division and proliferation
apoptosis which is programmed cell death
Mitosis increases the number of cells leading to growth. apoptosis remove unwanted cells and tissue. Cells undergoing apoptosis can also release chemical signals which stimulate mitosis leading to remodelling of tissue
Controlled by hox genes
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C19) What factors are affecting the expression of regulatory genes
Can be affected by the environment both internal and external
Stress can be defined as the condition produced When the homoeostatic balance between an organism is upset
Can be due to external factors such as a change in temperature or intensity of light. Internal factors can change due to the release of hormones or psychological stress impact during the growth and development
Drugs can affect the activity of regulatory genes for example the drug thalidomide
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C20) what is the definition of variation
As a result of mutations, changes to the genetic code which are random and constantly taking place
Essential for natural selection and therefore evolution
39
C20) what is chlorosis and how is it caused
When the leaves look pale or yellow occurs because the cells are not producing the normal amount of chlorophyll
Lack of chlorophyll reduces the ability of the plant to make food
Change in phenotype is the result of environmental factors
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C20 what are three examples of causes of chlorosis
Lack of light- when a toy or garden to his left on a lawn, with the absence of light plants will turn off the chlorophyll production to conserve resources
Mineral deficiencies- a lack of iron or magnesium. Iron is needed as a cofactor by some of the enzymes that produce chlorophyll and magnesium is found at the heart of the chlorophyll molecule. Plants that lack these elements simply cannot make chlorophyll
Viral infections- when the virus is infected plants they interfere with the metabolic system of cells. Common symptom is yellowing of the infected tissue as they cannot support synthesis of chlorophyll
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C20) How is animal body-mass an example of both genetic and environmental variation
The majority of cases dramatic variation in size such as obesity and being severely underweight or a result of environmental factors. (The amount of food eating, the quality of exercise
Obesity can be a result of the genetic make up of an organism
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c20) how does interspecific variation occur
Is determined by sexual reproduction involving meiosis and the random fusion of gametes at fertilisation
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C20) what is the definition of genotype
The combination of alleles an organism inherit for a characteristic
The genetic make up of an organism in respect of that gene
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C20) what is the definition of phenotype
The obvious characteristics of an organism
The actual characteristics that an organism displays are often Influenced by the environment.
Any changes the environment makes to a person are referred to as a modification
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C20 what is the definition of homozygous
They have two identical alleles for a characteristic
Homozygotes dominant- contains two dominant alleles for a particular phenotype
Homozygous recessive – contains two alleles for the recessive phenotype
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C20) what is the definition of heterozygous
They have two different alleles for a characteristic
The allele for the dominant phenotype will be expressed
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C20) what is the characteristic of continuous variation
Characteristic that can take any value within a range
There are two extremes, with every degree of variation possible in between
Height and weight
Many genes involved and the environment has a large effect
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C20)What is the definition of co-dominance
Occurs when two different alleles occurs for a gene-both of which are equally dominant
As a result both alleles of the gene are expressed in the phenotype of the organism
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C20) how do you write codominant crosses
A letter is chosen to represent the gene
The different alleles are then represented using a second letter which is shown as a superscript
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C20) what is the definition of multiple alleles,
Some genes have more than two versions
An organism can only carry two versions of a gene
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C20) how is sex determined
In humans sex is genetically determined
Humans have 23 pairs of chromosomes of varying sizes and shapes
In 22 pairs the members are the same
The 23rd pair known as the sex chromosome are different
Human females have 2 X chromosomes whereas males have an X and Y chromosome
The X-chromosome is large and contains many jeans not involved in sexual development.
The Y chromosome is very small containing almost no genetic information but does carry a gene that causes the embryo to develop as a male
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C20) what are the characteristics of sex linkage
Some characteristics are determined by genes carried on the sex chromosomes
These jeans are called sex linked
As the Y-chromosome is much shorter than the X-chromosome, there are a number of genes in the X-chromosome that males only have one copy of
meaning that any characteristics caused by a recessive allele on the section of X-chromosome which is missing the Y-chromosome occurs frequently in males
Females will have a dominant allele present in the other X-chromosome
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C20) what is the notation for sex linkage
The alleles are shown linked to the sex chromosome they are formed on with a superscript
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C20) What is the importance of a dihybrid cross
Used to show the inheritance of two different characteristics caused by two genes which may be located on different pairs of homologous chromosomes. Each gene can have two or more alleles
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C20 what is the expected ratio of a dihybrid cross
9:3:3:1
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C20) what are the reasons for the actual ratio of a genetic cross different to the expected ratio
The fertilisation of gametes is a random process so in a small sample a few chance events can lead to a skewed ratio
The genes being studied are both on the same chromosome. These are known as linked genes. If no crossing over occurs the alleles for the two characteristics always be inherited together
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C20)What is the meaning of autosomal linkage
Meaning that the genes are located on the same chromosome
Occurs on one of the 22 chromosomes
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C20) what is the meaning of autosomal linkage
When the genes that are linked are found on one of the other pairs of chromosomes
Cannot undergo normal random Shuffling of alleles during meiosis and expected ratio will not be produced in the offspring
The linked genes are inherited effectively as a single unit
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C20) What are the effects of autosomal linkage
Due to crossing over which results in the separation of some of the linked genes is the reason for the offspring not reaching the expected ratio
The closer the geans are on a chromosomes the less likely they are to be separated during crossing over and The fewer recombinant offspring produced
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C20) What is the meaning of recombinant offspring
They have different combinations of alleles than either parent
Occurs as a result of crossing over
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C20) What is the equation for recumbency frequency
Number of recombinant offspring/ total number of offspring
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C20) What is the recombination frequency
A measure of the amount of crossing over that has happened in meiosis
A recombination frequency of 50% indicate that there is no linkage and the genes are on separate chromosomes
Less than 50% indicates that the gene is linked and the random process of independent assortment has been hindered
The degree of crossing over is determined by how close the genes are on the chromosome, the closer they are the less likely they will be separated
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C20) What is the chi-squared test
Measures the size of the difference between the result you actually get (observed) and those you expected to get
Helps determine whether differences in the expected and observe results are significant or not
Used to test the null hypothesis: That there is no significant difference between expected and observed. Therefore is down to chance
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C20) what does a large chi-squared value mean
There is a statistically significance between the observed and expected results
Probability that these differences are due to chance is low
Must be a reason rather than chance for the unexpected result
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C20) What does it mean if the x2 value is less than the critical
There is no significant difference
We do not have significantly strong evidence to reject The null hypothesis
Therefore we accept the normal hypothesis, there is no significant difference between what we observed and what we expected
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C20) What does it mean if the x2 value is more than the critical
There is a significant difference
We reject the null hypothesis
Some other factor, outside our ordinary expectation is likely to be causing a significant difference between expected and observed
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C20 what is epistasis
The interaction of genes at different Loki
Gene regulation is a form of epistasis with regulatory genes controlling the activity of structural genes
Also occurs in biochemical pathways involving only structural genes
The characteristics of plants and animals that show continuous variation involve multiple genes and epistasis occurs frequently
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C20) How does epistasis occur
The products of a gene in a multi step pathway codes for an enzyme
the product of the enzyme acts as a substrate for the next enzyme
If the gene that produces the enzyme is not expressed then the intermediate molecule for the next reaction in the sequence is not produced
Therefore a lack of substrate for the next enzyme in the pathway and so the expression of this gene will not be observed in the phenotype
The gene is effectively masked by the lack of expression of the previous gene in the pathway
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C20) what is hypostatic and epistatic genes
A gene that is affected by another gene is said to be hypostatic
A gene that affects the expression of another gene is said to be epistatic
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C20) What is dominant and recessive epistasis
2 recessive alleles at the same gene Loki would cause epistasis
A dominant allele of the same gene Loki would cause epistasis
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C20) What is a gene pool
The sum total of all the genes in a population at a given time
The gene pool of a population include millions of jeans but you will look at the variation in the different alleles of a single gene within the gene pool
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C20) what is the allele frequency
The relative frequency of a particular allele in a population
The frequency an allele occurs in a population is not linked to whether it is codes for a dominant or recessive characteristic and is not fixed
Changes over time in response to changing conditions
Evolution involves a long-term change in the Allelle frequency of a population
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C20) how do you calculate allele frequency
The frequency of the dominant allele in the population is represented by the P
The frequency of the recessive allele in the population is represented by the q
Deployed breeding population with two potential alleles, the frequency of the dominant allele plus the frequency of the recessive allele always equals one
P+q=1
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C20) What does the hardy Weinberg principle state
In a stable population with no disturbing factors, the allele frequencies will remain constant from one generation to the next and there will be no evolution
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C20) What is the hardy Weinberg principle
P2 + 2pq +q2 = 1
P2 = frequency of homozygotes dominant genotype in the population
2pq = frequency of heterozygous genotype in the population
q2 = frequency of homozygous recessive genotype in the population
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C20) how do you do the hardy Weinberg equation
Work out the frequency of either the recessive or dominant genotype
Square root the frequency of either the recessive or dominant genotype
Work out what the frequency of either The recessive or dominant genotype using the equation P + Q = 1
Then plug it back into the equation after figuring out both the recessive and dominant genotypes
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C20) How can the hardy Weinberg principle be used to show disturbing the equilibrium
Assumes a theoretical breeding population of deployed organisms that is large and isolated, with random meeting, no mutations and no selection pressure of any type
In a natural environment these conditions virtually never occur. Species are continuously changing
These changes in allele frequency can be illustrated using the hardy Weinberg principle and upsetting the equilibrium may result in evolution
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C20) what factors affect evolution
Led by changes in the frequency of alleles within a population, leading to evolution
Mutation is necessary for the existence of different alleles in the first place and the formation of new alleles lead to genetic variation
Sexual selection leads to an increase in frequency of alleles which codes for characteristics that improve meeting success
Genetic flow is the movement of values between populations. Immigration and migration result in changes to a allele frequency within a population
Genetic drift occurs in small populations.A change in allele frequency due to the random nature of mutation. The appearance of a new allele will have a greater impact on a smaller population than in a much larger population where there is a greater number of alleles present in the gene pool
Natural selection leads to an increase in the number of individuals that have characteristics that improve their chances of survival. Reproduction rights of these individuals will increase as well the frequency of alleles coding for the characteristic. How changes in the environment can lead to evolution
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C20) how are larger population less affected by variation
The gene pool of a large population insures loads of genetic diversity owing to the presence of many different genes and alleles
Genetic diversity leads to variation within a population which is essential in the process of natural selection
Selection pressures lead to evolution
Population can adapt to change over time
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C20) how are Smaller population more affected by variation
Limited genetic diversity cannot adapt to changes as easily and are more likely to become extinct
A new strain of pathogen can wipe out the whole population
The size of a population can be affected by many factors
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C20) what are the two types of limiting factors of a population
Diversity dependent factors-are dependent on population size and increased competition, predation, parasitism and communicable diseases
Diversity independent factors-effect population of all sizes in the same way including: climate change, natural disaster, seasonal change and human activity
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C20) what is a population bottleneck
Large reduction in population size which lasts for at least one generation
The gene pool along with genetic diversity is greatly reduced and the effects will be seen in future generations
Takes thousands of years for genetic diversity to develop in a population through the slow accumulation of mutations
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C20) what are the positive aspects of genetic bottleneck
A beneficial mutation will have a much greater impact and lead to the quicker development of a new species
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C20) what is the founder affect
Small populations can arise due to the establishment of new colonies by a few isolated individuals
An extreme example of genetic drift
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C20) how does the founder affect affect genetic variation
The smaller populations have much smaller gene pools than the original population and display less genetic variation
If carried to the new population, the frequency of an allele that were rare in the original population will be much higher in the new, Smaller population and so they will have a much bigger impact during natural selection
86
C20) what are the different evolutionary forces
Stabilising selection
Directional selection
Disruptive selection
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C20)What is a normal distribution of a population
The traits or characteristics of a living organism shows variation within a population
The distribution of different variance will take the form of a bell shaped curve is plotted on a graph
Taking the birth weight of babies as an example
Babies with an average birth date will be the most common and therefore form the peak of the graph. Babies with very low-birth-weight are more prone to infections and very large babies result in difficult births
Both of the extremes in weight reduces the survival chances of the babies so the number of survival a very small or very large babies remain low form in the tails of the curve
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C20) What is Stabilising selection
Birthweight is natural selection at work. Babies with average birth weight are more likely to survive and reproduce than underweight or overweight babies
And example of stabilising selection because the norm or average is selected for (positive selection) and the extremes are selected against (negative selection)
Stabilising selection therefore results in reduction of the frequency of alleles at the extremes and an increase in the frequency of average alleles
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C20) what is directional selection
When there is a change in the environment and the normal phenotype is no longer than most advantages
Organisms which are less common and have more extreme phenotypes are positively selected.
The allele frequency then shift towards the extreme phenotype and evolution occurs
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C20) what is disruptive selection
The extremes are selected for and the non selected against
Opposite to stabilising selection when the norm is positively selected
91
C20) what is speciation
The formation of new species through the process of evolution
Organisms belonging to the new species will no longer be able to interbreed to produce fertile offspring with organisms belonging to the original species
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C20) what events lead to speciation
Members of the population become isolated and no longer interbreed with the rest of the population resulting in no gene flow between the two groups
Alleles within the groups continue to undergo random mutations. The environment of each group may be different or change so different characteristics will be selected for and against
Accumulation of mutations and changes in allele frequencies over many generations eventually lead to large changes in the phenotype. The members of the different populations become so different that they no longer able to interbreed to produce fertile offspring
They are now reproductively isolated and are different species
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C20) what is Allopatric speciation
Most common form of speciation
Happens when some members of a population are separated from the rest of the group by a physical barrier such as a river or the sea-geographically isolated
The environment of the different groups will often be different and so will the selection pressures resulting in different physical adaptations
Speciation of a small group will often result in the founder affect resulting in genetic drift further enhancing the differences between populations
94
C20) what is sympatric appreciation
Within populations that share the same habitat
Happens less frequently than Allopatric speciation and is most common in plants and animals
Can occur when members of two different species interbreed and form fertile offspring -often happens in plant
The hybrid formed, which is a new speciesWill have a different number of chromosomes to either parent and will no longer be able to interbreed with members of either parent population
This top gene flow and rapidly isolate the hybrid organism
95
C20) how are hybrid plants formed
Plants cross with plants of different species forming hybrids
Theindiscriminate release of large numbers of pollen grains by plants is one reason for this
The hybrids are reproductively isolated from each parent species but could still be present in the same habitat
Disruptive selection, making preference and other behavioural differences can result in individuals or small groups becoming reproductively isolated. However, still be living in the same habitat so gene flow , Even if reduce often interferes with the process of speciation
96
C20) what are the different reproductive barriers
Pre-zygotic reproductive barriers-prevent fertilisation or the formation of a zygote
Post psychotic reproductive barriers- As a result of hybridisation, reduce the visibility or reproductive potential of offspring
97
C20) what is artificial selection
Selective breeding is the same as natural selection except for the nature of the selection pressure applied
Instead of changes in the environment, it is the selection for breeding of plants or animals with desired characteristics by farmers or breeders
Farmers have selectively bred plants and animals since before genes were discovered or the theory of evolution was proposed
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C20) What are the steps to artificial selection
Individuals with desired characteristics are selected and interbred.
Offspring from this cross showing the best example of the desired traits are then selected to breed
This breeding of closely related individuals is calledinbreeding
The process is repeated over many generations resulting in changes to the frequency of alleles within the population and eventually speciation
99
C20) what are problems caused by inbreeding
Limiting the gene pool and so decreasing genetic diversity reducing the chances of a population of inbred organisms evolving and adapting to changes in the environment
Many genetic disorders are caused by a recessive alleles. Recessive alleles are not common in most populations but to recessive alleles are needed before they are expressed and most individuals will be heterozygous
Organisms that are closely related are genetically similar and are likely to have the same recessive alleles. The breeding of closely related organisms therefore result in offspring which have a greater chance of being homozygote For these recessive traits and being affected by genetic disorder
Overtime this reduces the ability for these organisms to survive and reproduce therefore the organism become less biologically fit-less likely to survive and produce two surviving offspring to replace them
100
C20) What are Gene Banks
See banks keep samples of seeds from both wild and domesticated variance. Important genetic resource
Gene Banks to biological samples, they are usually frozen
Because of problems caused by interbreeding, alleles from Gene Banks are used to create genetic diversity in a process called outbreeding
Breeding unrelated or distantly related varieties is also a form of outbreeding
Reduces the occurrence of homozygous recessives and increases the potential to adapt to environmental changes
101
C22) what is cloning
Asexual reproduction is a form of cloning
Results in offspring produced by mitosis
Clones are usually genetically identical to both the parent organism and each other
102
C22) What is vegetative propagation
Natural cleaning occurs in many species of flowering plants
Structural forms which develops into a fully differentiated new client, which is genetically identical to the parent
The new plant may be Propagated from the stem, leaf, board or root of the parent, depending on the type of plant, and it eventually becomes independent from its parent
Often involves perennating organs,Which enable pounds to survive adverse conditions. These contain stored foods from photosynthesis that can remain dormant in the soil. Often not only a means of asexual reproduction but also a way of surviving from one growing season to the next
103
C22) examples of when natural plant cloning occurs
Bulbs - The leaf bases swell with stored food from photosynthesis. Buds form internally which develop into new shoots and new plants in the next growing generation
Runners - A lateral stem grows away from the Parent plant and roots develop where the runner touches the ground. A new plant develops-the runner eventually withers away leaving the new individual independent
Stem tubers - The tip of an underground stem becomes swollen with stored food to form a tuba or Storage organ. Buds on the storage organs develop to produce new shoots
104
C22) how has natural cloning been used in horticulture
To produce new plants
Splitting up bulbs, removing young plants from runners
All increase plant numbers cheaply and the new plants have exactly the same genetic characteristics at their parents
It is possible to take cuttings from many plants-short sections of stems are taken and planted either directly into the ground or into pots. Rooting hormone is often applied to the base of the cutting to encourage the growth of new roots
105
C22) what are the advantages of propagation from cutting
It is much faster -The time from planting to cropping is much reduced
Guarantee the quality of the plants
By taking cuttings from good stock, the offspring Will be genetically identical and will therefore crop well
106
C22) what are the disadvantages of propagation from cutting
The lack of genetic variation in the offspring should any new disease or pest appear or if climate change occurs
107
C22) What is micropropagation using tissue culture
Micropropagation is the process of making large numbers of genetically identical offspring from a single parent plant using tissue cultureTechniques
108
C22) when is micropropagation using tissue cultures done
When a desired plant:
Does not readily produce seeds
Doesn’t respond well to naturalCloning
Is very rare
Has been genetically modified or selectively bred with difficulty
Is required to be pathogen free by growers
109
C22) what are the different ways that plants on micropropagated
With the use of sodium dichloroisocyanurate,The sterilising tablets used to make emergency drinking water. This keeps the plant tissues sterilised without being in a sterilised lab so it is extremely useful for scientist in the field of working with a rare and endangered plant material
Large is sterilising units
110
C22) What are the basic principles of micropropagation with tissue culture
Take a small sample of tissue from the plant you want to clone- the meristem tissue from shoot tips and axial buds are dissected out in sterile conditions to avoid contamination by fungi and bacteria. This tissue is usually virus free
The sample is sterilised, Usually by immersing it in sterilising agent such as bleach, ethanol and sodium dichloroisocyanurate. Which does not need to be rinsed off meaning the tissue is more likely to remain sterile. The material removed from the plant is called the explant
The explant is placed in a sterile culture medium containing a balance of plant hormones which stimulate mitosis. The cells proliferate, forming a mass of identical cells known as Callus
The callus is divided up and individual cells or clones from the callus are transferred to a new culture medium containing a different mix of hormones and nutrients which stimulate the development of tiny genetically identical plantlets
The plantlets are potted into compost where they grow into small plants
The young plants are planted out to grow and produce the crop
111
C22) what are arguments for micropropagation
Allows for the rapid production of large numbers of plants with non-genetic make up which will yield good crop
Makes it possible to produce viable numbers of plants after genetic modifications of plant cells
It produces a way of growing plants which are naturally relatively infertile or difficult to grow from seed
Culturing meristem tissue produces disease-free plants
112
C22)What are the arguments against micropropagation
It produces a monoculture-many plants which are genetically identical – so they are all susceptible to the same disease or changes in growing conditions
Relatively expensive process and requires skilled workers
If the source material is infected with a virus, all of the clones will also be infected
In some cases large numbers of new plants are lost during the process
113
C22) how does cloning in invertebrates occur
Can take several forms
Some animals can regenerate entire animals from fragments of the original if they are damaged
Flat worms and sponges fragment and form new identical animals as part of their normal reproductive process
Hydra Produce small buds on the side of the body which developed into genetically identical clones
Some insects, females can produce offspring without meeting –not true cloning
114
C22) how does cloning in vertebrals occur
Occurs in the formation of monozygotic twins
The early embryo splits to form two separate embryos. No one is sure of the trigger which causes this to happen
The frequency at which identical twins occur varies between species
When monozygotic twins are born although genetically identical, they may look different as a result of differences in their position and nutrients in the uterus
Some female reptiles and amphibians will produce offspring when no male is available. The offspring are often male rather than female, so they are not clones of their mother, all of the genetic material arises from her
115
C22) what is it like to artificially clone in animals
Relatively easy to produce artificial clones in some invertebrals-liquidise a sponge or chop up a starfish
Much more difficult to produce artificial clones for vertebrals
Two methods are now used widely in the production of high quality farm animals and in the development of genetically engineered animals for Pharming
116
C22) what are the two ways of producing vertebra artificial clones
Artificial twinning
Somatic cell nuclear transfer
117
C22) what is artificial twinning
After an egg is fertilised it divides to form a ball of cells. Each of these individual cells is Totipotent- it has the potential to form an entirely new animal
In natural twinning, an early embryo splits and 2 foetuses go on to develop from the two halves of the divided embryo. In artificial twinning the same thing happens but the early embryo is manually split
The early embryo may be split into more than two pieces and results in a number of individual offspring
Artificial twinning like embryo transfer which preceded it is used by the farming community to produce the maximum offspring from particularly good dairy or beef cattle or sheep
118
C22) what are the stages of artificial twinning in cattle
A cow with the desired trait is treated with hormones so she super ovulates, releasing more mature ova than normal
The ova must be fertilised naturally or by artificial insemination, by a ball with particularly good traits. The early embryos are gently flushed out of the uterus
Alternatively, the mature eggs are removed and fertilised by top quality bull semen in the lab
Usually before or around Day 6, when the cell are still Totipotent, The cells of the early embryo Are split to produce several smaller embryos, each capable of growing onto form a healthy food term calf
Each of the split embryos are grown in the lab for a few days to ensure all is well before it is implanted into a surrogate mother. Each embryo is implanted into a different mother as single pregnancies carry lesser risk than twin pregnancies
The embryos develop into foetuses and are born normally, so a number of identical cloned animals are produced by different mothers
119
C22) why do some farmers freeze the embryos
This allows the success of a particular Animal to be assessed and if the stock is good, remaining identical embryos can be implanted and bought to term
120
C22) what is somatic cell nuclear transfer
Artificial twinning clones an embryo
now possible to clone an adult animal by taking the nucleus of an adult stomatic (body) cell and transferring it to an enucleated egg cell (Nucleus removed)
Tiny electrical shock is used to fuse the egg and nucleus, stimulate the combined cell to divide and form an embryo that is a clone of the original adult
Animals of different breeds are often used as the cell donor, the egg donor and the surrogate mother to make it easier to identify the original animal at each stage
121
C22)What are the stages of Stomatic cell nuclear transfer
The nucleus is removed from a stromatic cell of an adult animal
The nucleus is removed from a mature ovum harvested from a different female animal of the same species
The nucleus from the adult somatic cell is placed into the enucleated ovum and given a mild electric shock so it fuses and begins to divide. In some cases the nucleus from the adult is not removed-it is simply placed next to the enucleated ovum and the two cells fuse (electrofusion) and begin to divide under the influence of the electrical current
The embryo that develops is transferred into the uterus of a third animal where it develops to turn
The new animal is a clone of the animal from which the original somatic cell is derived although the mitochondrial DNA will come from the Egg cell
122
C22) What are the uses of stromatic cell nuclear transfer
Used in pharming-The production of animals which have been genetically engineered to produce therapeutic human proteins in their milk
Can be used to produce genetically modified animals which grow organs that have the potential to be used in human transplant
123
C22) what are the advantages of animal clothing
Artificial twinning enables high yielding farm animals to produce many more offspring than normal reproduction
Artificial twinning enables the success of a male animal at passing on desired genes to be determined. If the first cloned embryo results in a successful breeding animal, more identical animals can be raised from the remaining frozen clones
Somatic cell nuclear transfer enables genetically modified embryos to be replicated and to develop, giving many embryos from one engineering procedure. Important process in parming
Somatic cell nuclear transfer has the potential to enable rare, endangered or even extinct animals to be reproduced. The nucleus from dried or frozen tissue can be transferred to the egg of a similar living species to produce clones
124
C22) What are the disadvantages of animal clothing
Somatic cell nuclear transfer is very ineffective process-most animals it takes many eggs to produce a single cloned offspring
Many crowned animal embryos failed to develop and miscarry or produce malformed offspring
Many animals produced by cloning have shortened lifespan
Somatic cell nuclear transfer has been relatively unsuccessful so far in increasing the population of rare organisms or allowing extinct species to be brought back to life
125
C22) what are the reasons for using microorganisms
There are no welfare issues to consider –all data needed is the optimum conditions for growth
There is an enormous range of micro organisms capable of carrying out many different chemical synthesis or degradation that can be used
Genetic engineering allows us to artificially manipulate micro organisms to carry out synthesis reactions that they do not normally do
Micro organisms have a very short life-cycle and rapid growth rate. As a result given the right conditions huge quantities of microorganisms can be produced in a short period of time
126
C22) what does indirect food production
Micro organisms are widely used in biotechnological processes to make food
Micro organism have an indirect effect-it is the action on other food that is important
127
C22) how does baking occur
Yeast mixed with sugar and water to respire aerobically. Carbon dioxide produced makes bread rise
Active yeast is mixed with other ingredients and left in warm environment to rise
Cooked in the oven-the carbon dioxide bubbles expand so the bread rises more. Yeast cells are killed during cooking
128
C22)How does brewing occur
Yeast respire anaerobically to produce ethanol. Traditionally yeast Firment at20 to 28°C but genetically modified yeast Firment at lower and therefore cheaper, temperatures and clamped together and sink at the bottom of the process
Malting-enzymes that break down starch molecules down to sugar which yeast can use. Seeds then killed by slow heating but enzyme activity retained to produce malt
Mashing -The mould is mixed with hot water and enzymes break down starch is to produce Wort. Hops are added for favour and antiseptic qualities. The wort sterilised and cold
Fermentation -Wort is inoculated with yeast. Temperature maintained for optimal anaerobic respiration. Yeast is inhibited by falling temperature and lack of oxygen
Maturation -The beer is Conditioned for days in tank
Finishing-beer is filtered, pasteurised and then bottled
Alcohol content varies between 4% and 9%
129
C22) how does cheesemaking occ
Bacteria feed on lactose in milk changing the texture and taste and inhibiting the growth of bacteria which make milk go off
Milk is pasteurised killing off most natural bacteria and homogenised, The fat droplets evenly distributed in milk
Mixed with bacterial cultures and sometimes enzymes and kept until the milk separates into solid curds and liquid whay
The curd are cut and cooked in the whay then strain through draining moulds. Whay used as animal feed
The curd are put into steel or wooden drums and may be pressed. They are left to dry, mature and ripen before eating as the bacteria continue to act.
130
C22) how does yoghurt making occur
Bacteria often forms ethanol And lactic acid. Both produce extracellular polymers that give yoghurt its smooth thick texture
Skimmed milk powder is added to milk and the mixture is pasteurised and homogenised and cooled
The milk is mixed with a 1:1 ratio of the two bacterial and incubated
At the end of the fermentation the yoghurt may be put into cartons at a lower temperature
Thickset yoghurts are mixed and Ferment in the pot
Yoghurt has a shelf life of about 19 days
131
C22) what is direct food production
People have eaten fungi for thousands of years in the form of mushrooms. Facing potential protein shortage around the world scientists are developing more ways of using micro organisms to directly produce protein that we can eat known as single celled protein
QuranMade of single celled fungus that is grown in large fermenters using glucose syrup as a food source. The microorganisms are combined with albumen(Egg white) then compressed and formed into meat substitutes
Not suitable for vegetarians but a healthy choice as it is high in protein and low in fat
People are very conservative in their food choices and the new food was launched without the mention of fungi being used in its production
132
C22) what are the advantages of using micro organisms to produce human food
Microorganisms reproduce fast and produce protein faster than animals and plants
Micro organisms have a high protein content with little fat
Can be genetically modified to produce the protein required
Production of micro organisms is not dependent on whether, breeding cycle
No welfare issues when growing microorganisms
can be made to taste like anything
133
C22)What are the disadvantages of using micro organisms to produce human food
Some micro organisms can also produce toxins if the conditions are not maintained and the optimum
The micro organisms have to be separated from the nutrient broth and processed to make the food
Often involve genetic manipulated organisms and many people have concerns about eatingGenetically modified food
The protein has to be purified to ensure it contains no toxins or contaminants
Has little natural flavour
134
C22) why is penicillin produced the way it is produced
The Mould needs relatively high oxygen levels and a rich nutrient medium to grow well
Sensitive to pH and temperature affecting the way it has produced commercially
Semi continuous batch process is used.
135
C22) How is penicillin produced
First stage of the production process the fungus grows
The second stage it produces penicillin
Finally, The drug is extracted from the medium and purified
The process uses relatively small fermenters because it is very difficult to maintain high levels of oxygenation in very large bioreactors
The mixture is continuously stirred to keep it oxygenated
There is a rich nutrient medium
Growth medium contains a buffer to maintain pH around 6.5
The bioreactors are maintained at 25 to 27°C
136
C22) why is insulin produced the way it is produced
People with type one diabetes and some people with Type II diabetes regularly inject insulin to control blood sugar levels
In the past insulin was extracted from the pancreas of animals usually pigs or cattle slaughtered for meat.
This meant the supply was erratic because it depended on the demand for meat – when few animals were killed less insulin was available but the number of peopleWith diabetes stayed the same
Some people were allergic to the animal insurance as it was often in pure, very pure forms were developed to overcome the problem
peak activity of animal Insulin is several hours after the injection making calculations when to eat meals difficult
Some faith groups using pig products was not permitted
137
C22)How is insulin produced
Genetically engineered bacteria can make human insulin
Bacteria are grown in fermenters and downstream processing results in a constant supply of pure human insulin
138
C22) what is bioremediation
Micro organisms are used to Breakdown pollutants and contaminants in soil or in the water
Byron mediation takes place on the site of contamination, sometimes material is removed for decontamination
Most cases natural microorganisms outperform genetically modified ones
139
C22) what are the different approaches to bioremediation
Using natural organisms- many microorganisms naturally break down organic material producing carbon dioxide and water. Soil and water pollutants are often biological
if naturally occurring Microorganisms are supported they will break down and neutralise many contaminants. By adding nutrients to encourage microbial growth
Genetically modified organisms-scientists are trying to develop genetically modified bacteria which can break down contaminants which they could not naturally encounter for example mercury. Aim is to develop filters containing these bacteria
140
C22) why must the correct health and safety procedures be followed even when the microorganisms are expected to be Harmless
Always the risk of mutations taking place, making the strain pathogenic
May be contamination with pathogenic microorganisms from the environment
141
C22) how do you culture microorganisms
Micro organisms need food as well as the right conditions of temperature, oxygen and pH
Food provided for micro organisms is best known as the nutrient medium
Either in liquid form (broth) or in solid form (agar)
Nutrients are often added to these to provide a better medium for microbial growth
Some microorganisms need precise balance of nutrients but often the medium is enriched with good protein sources
Enriched nutrient medium allows samples containing a small number of organisms to multiply rapidly
The nutrient medium needs to be kept sterile until it is ready to use using aseptic techniques are important
142
C22) What is the process of inoculation
Once the nutrient medium is prepared the bacteria must be added in this process
143
C22) how do you inoculate broth
Make a suspension for the bacteria to be prone
Makes a known volume with the sterile nutrient broth in the flask
Stopper the flask with cotton wall to prevent contamination from the air
Incubate at a suitable temperature, shaking regularly to aerate the broth providing oxygen for the growing bacteria
144
c22)How do you inoculate agar
The wire inoculating loop must be sterilised by holding it in a Bunsen burner until it glows red hot. Not be allowed to touch any surface as it caused to avoid contamination
Did the sterilised loop in the bacterial suspension. Remove the lid of the petri dish and make a zigzag streak across the surface of the agar. Avoid the loop digging into the agar by holding it almost horizontal. The surface of the agar must be kept intact
Replace the lid of the petri dish. Should be held down with tape but not completely sealed so oxygen can get in, preventing the growth of anaerobic bacteria. Incubate at suitable temperature
145
C22)What are the four stages of the growth curve of bacteria
The lag phase when bacteria are adapting to the new environment. They are growing, synthesising the enzymes they need and are not yet reproducing at the maximum rate
The log or exponential phase when the rate of bacteria reproduction is close to or at its theoretical max
The stationary phase occurs when the total growth rate is zero-the number of new cells formed by binary fusion is cancelled down by the number of cells dying
The decline or death Phase comes when reproduction has almost seized and the death rate of cells is increasing
146
C22)What are several limiting factors which prevent exponential growth in a cultural of bacteria
Nutrients available- initially plenty of food but as the number of organisms multiply exponentially it is used up. Nutrient level become insufficient to support further growth and reproduction
Oxygen level- as the population rises, so does the demand for respiratory oxygen
Temperature- enzyme controlled reactions within microorganisms are affected by the temperature of the culture medium. Slower temperatures slowdown growth and reproduction higher temperatures speeded up to an extent and then it denatures the enzyme killing the microorganism
Buildup of waste- as bacteria numbers rise, buildup of toxic material may inhibit further growth and even poison and kill the culture
Change in pH- carbon dioxide produced by respiration increases the pH of the culture falls until a point where the low pH affects enzyme activity and inhibit population growth
147
C22) what are primary and secondary metabolites
You want as much micro organisms as possible because the microorganisms itself is the product to be sold
Primary metabolite are substances which form an essential part of the normal functioning of a micro organism
Secondary metabolites are substances which are not essential for normal growth but are still used by cells and are often the required product in a bioprocess
148
C22) what are the types of bioprocesses
Two of the main ways of growing microorganisms are batch fermentation and continuous fermentation
Depends on the Micro morganism chosen and the ideal size and shape of the bioreactor
149
C22) what are the stages of batch fermentation
That micro organisms are inoculated into a fixed volume of medium
As growth takes place, nutrition are used up and Both new biomass and waste products buildup
As the cultures reach the stationary phase overall growth Ceases but during this phase The micro organisms often carry out biochemical changes to form the desired and product
The process is stopped before the death phase and the product is harvested. The whole system is then cleaned and sterilised and a new batch culture started up
150
C22) what are the stages of continuous culture
Micro organisms are inoculated into sterile nutrient medium and start to grow
Sterile nutrient medium is added continuously to the culture once it reaches exponential point across
Culture broth is continuously removed - the medium, waste product, micro organisms and products-keeping the cultural volume in the bioreactor constant
Enables continuous balanced growth with levels of nutrients, pH and metabolic products kept more or less constant
151
C22) what is the importance of bioreactors in culturing on an industrial level
Both methods of operating a bioreactor can be adjusted to ensure either the maximum product of the biomass or the maximum product of the primary secondary metabolite
Adapted for maximum yield of metabolites.
Majority of industrial processes used batch or semi continuous cultivation
Continuous calculation is largely used for the Production of single celled protein and in some waste water treatment processes
All bioreactors produce a mixture of unused natural Broth, micro organisms, primary metabolites, second metabolites and waste products
Useful parts of the mixture has to be separated out by downstream processes
152
C22) what are the factors that need to be controlled in a bioreactor
Temperature- if the temperature is too low the micro organism will not grow quickly enough. If the temperature is too high the enzyme start to the nature and the micro organisms are inhibited or destroyed.
They often have heating and cooling system is linked to temperature sensors and a negative feedback system to maintain optimal conditions
Nutrients and oxygen- oxygen and nutrition mediums can be added in controlled amounts to the broth when probes or sample tests indicate the levels are dropping
Mixing things up- inside are large volumes of liquid which may be quite thick and viscous due to the growth of microorganisms.
Simple diffusion is not enough to ensure all microorganisms receive enough food and oxygen all the mixture is kept at the right temperature
Most bioreactors have a mixing mechanism and many are stirred continuously
Asepsis- Contamination by Micro organisms from the air or from workers can affect the yield.
Most bioreactors are sealed, aseptic units. If the process involves genetically engineered organisms it is legally required to be contained in the bioreactor
153
C22) what are the advantages of using isolated enzymes instead of the whole of the whole organism
Less wasteful- whole organisms use up substrate growing and reproducing. Producing biomass rather than product. Isolated enzymes do not
More efficient- isolated enzymes work at a much higher concentration than is possible when they are part of the whole microorganism
More specific- no unwonted enzymes present, no wasteful side reactions take place
Maximise efficiency- isolating enzymes can be given ideal conditions to maximise product formation, which may differ from those needed for the growth of the whole organism
Less downstream processing- pure product is produced by isolated enzymes. Whole organism gives a variety of products in the final breath, making isolation of design products more difficult and therefore expensive
154
C22)Why are extracellular enzymes for micro organisms used as isolation enzymes instead of intracellular
Generally easier and therefore cheaper
Extracellular enzymes are secreted making them easy to isolate and use
Each micro organism produces relatively few extracellular enzyme making it easy to identify and isolate the required enzyme. In comparison each Micro organism produces hundreds of intracellular enzymes which would need extracting from the cell and separating
Extracellular enzymes tend to be more robust than intracellular enzymes. Conditions outside a cell are less tightly controlled then conditions in the cytoplasm, so extracellular enzymes are adapted to cope with greater Variation in temperature and pH then intracellular enzymes
155
C22) when are intracellular enzymes used
Because of the bigger range of intracellular enzymes
They can provide the ideal enzyme for a process
The benefits of using and very specific intracellular enzymes outweigh the disadvantages of the more expensive extraction and isolation process needed for the more tightly controlled conditions
Penicillin actlase for converting natural penicillin into semi synthetic drug
156
C22) what are immobilising enzymes
Isolated enzymes are More efficient than whole organisms but using three enzymes is often very wasteful
Enzymes are not cheap to produce but at the end of the process they cannot usually be recovered and so simply lost
Increasingly enzymes in industrial processes are immobilised-attached to and inert support system over which the substrate passes and is converted to product
Technology mimicking nature- enzyme in cells are usually bound to membranes to carry out the repeated cycle of catalase
Immobilised enzymes are held stationary during the catalase process can be recovered from the reaction mixture and used time after time
The enzymes do not contaminate the end product,Less downstream processing is needed
Process more economical
157
C22) what are the advantages of using immobilised enzymes
Enzymes can be Reused-cheaper
Easily separated from the reactants and products of the reaction they are catalysing - reduced downstream processing-cheaper
More reliable- high degree of control over the process as the insoluble support provides a stable microenvironment for the immobilised enzyme
Greater temperature tolerance- immobilised enzymes are less easily denatured by heat and work at optimum levels over a much wider range of temperatures, making bioreactors less expensive to run
Easy to manipulate- the catalytic properties of immobilised enzymes can be altered to fit a particular process much easily than those of free enzymes. Keep bioreactors running continuously for longer periods without emptying or cleaning helps to keep costs down
158
C22) what are the disadvantages of using immobilised enzymes
Reduced efficiency- process of immobilising an enzyme may reduce its activity rate
Higher initial costs of materials- immobilised enzymes are more expensive than free enzymes or micro organisms but unlike three enzymes immobilised enzymes do not need to be repeatedly replaced
Higher initial cost of bioreactors- system needs to use immobilised enzyme is different from traditional fermenters so they are costly initially
More technical issues- reactors which use immobilised enzymes are more complex than simple fermenters- more things can go wrong
159
C22) what are the different ways that enzymes are immobilised
Surface immobilisation- absorption to inorganic carriers
Surface immobilisation – covalent or ionic bonding to inorganic carriers
Entrapment- in the matrix
Entrapment-membrane entrapment in microcapsules or behind a semipermeable membrane
160
C22) what are the advantages and disadvantages of surface immobilisation through absorption to inorganic carriers
Simple and cheap to do
Can be used in many different processes
Enzymes very accessibility to substrate and the activity is virtually unchanged
Enzymes can be lost from matrix relatively easily
161
C22) what are the advantages and disadvantages of surface immobilisation through covalent or ionic bonding to inorganic carriers
Cost varies
Enzymes are strongly bound and therefore unlikely to be lost
Enzymes very accessibility to substrate
PH and substrate concentration often have little effect on enzyme activity
Cost varies
Active site of the enzyme may be modified in process making it less effective
162
C22) what are the advantages and disadvantages of Entrapment-in the matrix
Widely applicable to different processes
May be expensive
Can be difficult to entrap
Diffusion of substrate to and product from the active site can be slow and hold up the reaction
Effects of entrapment on enzyme activity very variable, depending on matrix
163
C22) what are the advantages and disadvantages of Entrapment-in Micro capsules or a semipermanent membrane
Relatively simple to do
Relatively small effect on enzyme activity
Widely applicable to different processes
Relatively expensive
Diffusion of the substrate to and product from the active side can be slow and hold up the reaction
164
C22) what are examples of using immobilised enzymes
Immobilised glucose isomerase used to produce fructose from glucose.Fructose is sweeter than sucrose or glucose and widely used as a sweetener in food production.
Immobilise lactase used to produce lactic free milk. Some people and cats are lactose intolerant. Immobilised lactase hydrolysis lactose to glucose and galactose giving lactose free milk
Immobilised aminoacylase -Produce a pure source of L amino acid used in the production of pharmaceuticals
165
C21) how do you produce a DNA profile
Extract the DNA
DNA must be extracted from a tissue sample, at the start it had to be large samples. Now using a technique called polymerise chain reaction, the thinnest fragment of tissue can be give scientist enough DNA for a profile
Digest the sample
Strands of DNA or cut into small fragments using special enzymes called restriction endonucleases .Different Restriction endonuclease Cut DNA at specific nucleus sequences known as a restriction site or recognition site. All restriction endonuclease make 2 cut one through each strand of DNA double helix.
Restriction endonuclease gives scientist the ability to cut DNA strands and defined points in the introns
Separate the DNA fragments
The cut fragments of DNA need to be separated to form a clear and recognisable pattern. Damage using electrophoresis, utilising the way charged particles move through a gel medium under the influence of electrical currents. Larger DNA strands move further down. Gel immersed in alkali in order to separate the DNA double strands into single strands. Single-stranded DNA fragments transferred into a membrane for southern blotting
Hybridisation
Radioactive or fluorescent DNA probes are now added in excess to the DNA fragments on the membrane. DNA probes are short DNA or mRNA sequence is complimentary to a known DNA sequence. They bind to the complimentary strand of DNA called hybridisation
See the evidence
Radioactive labels were added to the DNA probe, x-ray images are taken of the paper/membrane. If fluorescent labels were added to the DNA probe the paper/membrane would be placed on the UV lights so the fluorescent tags glow-Most common used today. Fragments give a pattern of bars-DNA profile-unique to every individual
166
C21) how do you set up polymerise chain reaction
The DNA sample to be amplified, and excess of the four nucleotide bases A, T, C and G, Small primer DNA sequence and the enzyme DNA polymerase are mixed in a violent that is placed in a PCR machine
167
C21)What is the importance of the PCR machine
The temperature within the PCR machine is carefully controlled and changes rapidly and programmed intervals triggering different stages of the process
The reaction can be repeated many times by the PCR machine through the program temperature settings
168
C21) what are the stages of polymerised chain reaction
Separating the strands
PCR machine increases to 90 to 95°C denaturing the DNA by breaking the hydrogen bonds holding the DNA strands together so they separate
Annealing the primer
Temperature is decreased to 55 to 60°C and the primer bind (annuals) to the end of the DNA strands needed for the replication of the strand to occur
Synthesis of DNA
Temperature increased to 72 to 75°C as it is the optimal temperature for DNA polymerase to work best. DNA polymerase adds bases to the prime of building up complimentary strands of DNA and producing double-stranded DNA identical to the original strand
169
C21)What are the uses of DNA profiling
Field of forensic science especially criminal investigation. Performing on traces of DNA left at the crime scene
Use to prove paternity of a child when it is in doubt
Identifying individuals who are at risk of particular diseases
170
C21) how is DNA sequencing set up
The DNA is chopped into fragments and each fragment is sequenced new power
The process involves terminator bases, modified versions of the 3 nucleotide bases which stop DNA synthesis when they are included.
A terminator. DNA synthesis at the location that a base would be added, a C terminator where a C base would go
Terminator bases are given a colour fluorescent tag
171
C21) What are the stages of DNA sequencing
The DNA for sequencing is mixed with a primer, DNA polymerase, and excess of normal nucleotides and terminator bases
The mixture is placed in a thermal cycler that rapidly changes temperature and programmed intervals in repeated cycles, the double-stranded DNA separates into single strands, the primer anneal to the DNA strand
DNA polymerase starts to build up new DNA strands by adding nucleotides with the complimentary base of the single-stranded DNA template
Each time a terminated base is incorporated instead of a normal nucleotide, the synthesis of DNA is terminated as no more basis can be added. The chain terminating bases are present in lower amounts and are added at random this results in many DNA fragments of different lengths depending on where the chain terminating bases have been added during the process. After many cycles all the possible DNA chains will be produced with the reaction at every base. DNA fragments separated by length using capillaries sequencing like electrophoresis in capillaries tubes. The fluorescent terminator bases are used to identify the final base of each fragment. Lasers detect the different colours and the order of the bases
The order of bases in the capillary tubes showed the sequence of the new complimentary strand of DNA which had been made.Used to build up the sequence of the original DNA strand
The data from the sequencing processes fed into a computer that resembles the genome by comparing all the fragments and finding the areas of overlap between them
172
C21) what is the next generation of sequencing
Instead of using a gel or capillary, the sequencing reaction takes place on a plastic slide known as a flow cell
Millions of fragments of DNA are attached to the slide and replicated in situ using PCR to form clusters of identical DNA fragments
Still uses the principle of adding a coloured terminator base to stop the reaction so an image can be taken
As all of the clusters have been sequenced and imaged at the same time the technique is known as massively parallel sequencing
173
C21) what is the meaning of bioinformatics
Is the development of the software and computing to is used to organise an analyse raw biological dataIncluding the development of algorithms, mathematical models and statistical test to help us to make sense of the enormous quantities of data being generated
174
C21) what is Computational biology
Uses this data to build theoretical models of biological systems, which can be used to predict what will happen in different circumstances
Computational biology is the study of biology using computational techniques, especially in the analysis of huge amounts of biodata
175
C21) what is genomics
The field of genetics that applies DNA sequencing methods and computational biology to analyse the structure and function of genomes
176
C21)How has the human genome been analysed
Computers can analyse and compare the genome of many individuals, revealing patterns in the DNA we inherit and the diseases of which we are vulnerable
Enormous implication for health management and the field of medicine in the future. Genomic‘s is changing the face of epidemiology
Scientists increasingly recognise with the exception of a few relatively rare genetic diseases caused by changes in single genes, our genes work together with the environment to affect our physical characteristics, our physiology and all likelihood of developing certain diseases
177
C21) How has sequencing the genomes of pathogens becoming fast and relatively cheap enabled doctors to do
Find out the source of an infection
Identify antibiotic resistant strains of bacteria, ensuring antibiotics are only used when they will be effective and help prevent the spread of antibiotic resistance
To tackle the progress of an outbreak of potential Serious diseases and monitor potential epidemics
To identify regions in the genome of pathogens that may be useful targets in development of new drugs and to identify genetic markers for use in vaccines
178
C21) how can scientists identify species
Using traditional methods of observation, it can be very difficult to determine which species an organism belongs to or if a new species have been discovered.
Gene analysis provides scientist with another tool to aid in species identification by comparing to a standard sequence for the species
Challenge for scientists is to produce stock sequences for all the different species.
Useful technique is to identify particular sections of the genome that are common to all species but vary between them, so comparison can be made –DNA barcoding
Scientists identified species using relatively short sections of DNA from a conserved region of the genome
For animals the region chosen is a 648-based pair section of the mitochondrial DNA in the gene cytochrome C oxidise, that codes for an enzyme involved in cellular respiration. This section is small enough to be sequenced quickly and cheaply yet varies enough to give clear differences between species
Inland plants, this region of DNA does not evolve quickly enough to show clear differences between species but two regions in the DNA of the chloroplast have been identified that can be used in a similar way to identify species
179
C21) what is the problem with the barcode in the system
Scientists have not come up with a suitable region for fungi and bacteria and they may not be able to do so
Had a big impact on classification
180
C21) How has gene sequencing become a powerful tool for evolution relationships between organisms
DNA sequences of different animals can be compared because the basic mutation rate of DNA can be calculated scientists can calculate how long ago to species diverged from a common ancestor
DNA sequencing enable scientists to build up evolutionary trees with an accuracy like never before
