Powerpoint 1 Flaskcards

Question 1

What are the types of mutations

Answer 1

Point mutations- one base pair is replaced by another
Insertion and deletion- one or more nucleotides are inserted or deleted from a length of DNA, causes a frame shift

Question 2

How mutations occur

Answer 2

‘Spontaneously’ when DNA is being replicated

Exposure to a mutagen- chemicals e.g. tar and ionising radiation( UV and x-rays)

Mutations associated with mitosis (somatic mutations), these aren’t genetically inherited, result of aging or contribute to cancer formation

Mutations during meiosis are inherited (gametes)
*risk is reduced by G1 and G2 checkpoints

Question 3

Ionsizing radiation

Answer 3

Physical mutagen
Break one or both strands of DNA, sometimes this damage is repaired by proteins in the cell, but mutations can occur during this

Question 4

Deaminating agents

Answer 4

Chemical mutagen
Chemically alter the bases in DNA such as converting cytosine to uracil in DNA- this alters the bases sequence

Question 5

Alkylating agents

Answer 5

Biological agent which acts as a mutagen
Methyl or ethyl groups are attached to bases resulting in the incorrect pairings of bases during replication

Question 6

Base analogues

Answer 6

Biological agent which acts as a mutagen
Incorporated into DNA in place of the usual bases during replication, this changes the base sequence

Question 7

Viruses

Answer 7

Biological agent which acts as a mutagen
Viral DNA may insert itself into a genome, changing the base sequence

Question 8

Types of mutation: gene

Answer 8

Genetic change affecting the bases during sequence of a single gene
Gene mutation may result in the formation of a new allele

Question 9

Types of mutations: chromosome

Answer 9

Block:
change in the structure of a chromosome involving large pieces being rearranged, causes whole groups of genes to be affected
Number:
-aneuploidy- the gain or the loss of. Whole chromosome (Down syndrome)
-polyploidy- the loss or the gain of complete sets of chromosomes

Question 10

Types of chromosomal mutations

Answer 10

Duplication, deletion, translocations, non disjunction, inversions

Question 11

Duplication

Answer 11

Copying of several or a single repeated gene. Associated with the development of diseases and relate to the genes and chromosomes that the duplication occurs in

Question 12

Deletion

Answer 12

Where segments of chromosomes are lost

Question 13

Translocation

Answer 13

Can cause Down syndrome where 14 and 21 autosomes are involved

Question 14

Non disjunction

Answer 14

Where the homogous chromosomes are not separated or chromatids during the process of meiosis

Question 15

Inversions

Answer 15

The subject of a lot of research still ongoing. Inversions do exist in healthy genomes, and are being characterised. Effects are still unknown

Question 16

Effects

Answer 16

No effect- no effect on phenotype of the organism because normal functions proteins are still synthesised, if there was a change to the amino acid sequence it had no overall effect on its function

Damage/harmful- phenotype of the organism is negatively effected because they protein is no longer synthesised or synthesised but has no function, this interferes with one or more essential function

Beneficial- sometimes he protein which results from the change offers a selective advantage, useful characteristic is observed in the organisms phenotype

Question 17

Point mutations: three types of point mutations

Answer 17

Silent- codes for the same amino acid, genetic code is generate , change in the base but still codes for the same amino acid, no impact on function of the protein
Missence- codes for a different amino acid in primary sequence- two types
Non sense- codes for a stop codon, doesn’t code for an amino acid- truncated proteins (muscular dystrophy)

Question 18

The two types of missence

Answer 18

Conservative- no impact on the function of the protein, R group could have the same function, so the same bonds are formed in tertiary structure Amino acid changed away from functioning part of the protein- no impact.
Non conservative- non functioning protein produced e.g sickle cell anaemia

Question 19

Indel mutations

Answer 19

Where a base is inserted or deleted, al subsequent base triplets are altered (frameshift) ‘downstream’

Question 20

Partial frame shift

Answer 20

One is inserted and one is deleted so only a portion of the amino acid has a frame shift

Question 21

Beneficial

Answer 21

Drive evolution of the organism, successful mutations are passed down to offspring, mutations make alleles

Question 22

Neutral

Answer 22

No benefit or disadvantage, so their frequency of alleles in the population remain stable as it isn’t being selected for or against by the environment

Question 23

Gene regulation

Answer 23

Process by which genes are switched on or off
- When a gene is switched on than the gene is being transcripted and the protein product will be being -manufactured at the ribosomes after translation for a cellular process
Gene switched off then its not being transcribed, stop or decrease the production of the protein

Question 24

Four categories of gene regulation

Answer 24

Transcriptional- affects the process of transcription directly, it can be switched on and off
Post transcriptional- mRNA editing
Translational- starting or stopping translation
Post translational- modifying the proteins to increase or decrease their activity

Question 25

Prokaryotes

Answer 25

Organise their genes into structures called operons (lac operon)

Question 26

Transcriptional control

Answer 26

Histone modification- add methyl- heterochromatin- positive charge Histone modification- add acetyl or phosphate- euchromatin- negative charge Transcription factor- aid binding of RNA polymerase

Question 27

Chromatin and Epigenics

Answer 27

DNA wrapped around histones are called chromatin Epigenics is used to describe gene control by modification of DNA or DNA processes

Question 28

Heterochromatin

Answer 28

Doesn’t usually undergo gene expression, because the RNA polymerase is unable to unwind the DNA and access the base sequence to copy

Question 29

Euchromatin

Answer 29

Is freely operational Ensures the unnecessary protein synthesis doesn’t occur during mitosis

Question 30

Transcription factors

Answer 30

Proteins that bind to eukaryotic promoters, usually small proteins that have a complentary shape to the promoter in question Binding of the transcription factor allows RNA polymerase to bind to the gene more effectively

Question 31

Histone modification

Answer 31

Acetylation- adds a more negative charge the histones and cause the DNA to pack less tightly Methylation and phosphorylation- makes histones more hydrophobic and more tightly to each other causing DNA to be more coiled

Question 32

Post transcriptional control

Answer 32

Cap and tail pre mRNA Splice pre mRNA- remove introns and join exons together forming more mature mRNA

Question 33

Translational control mechanisms

Answer 33

Adds molecules to aid binding to ribosomes- promote translation Molecules to stop binding to ribosome or increase breakdown by exonuclease enzymes, stops translation

Question 34

Post translational control

Answer 34

Proteins produced are inactive, activate proteins by phosphorylation- adds a phosphate

Question 35

Homeotic gene subset

Answer 35

A subset of homeotic gene is called homeobox genes which contain 180 base pair length of DNA called Homeobox

Question 36

Morphogenesis

Answer 36

Is a term used to regulate anatomical development in the organism

Question 37

Homeobox genes

Answer 37

They are found in plants, animals and fungi Genes which govern body plans and contain a characteristic section of DNA, codes for a specific sequence of 60 amino acids with the synthesised protein called a homeodomain, the sequence folds in the specific shape consisting of three A helices

Question 38

Hox genes

Answer 38

Only found in animals Correct positioning of body parts

Question 39

Structure of a homeobox

Answer 39

The second and third helix crest a helix turn helix which insists of two A helices connected by a short loop of amino acids

Question 40

Homeobox mutations

Answer 40

Developmental abnormalities- irregular shaped organs and features or incorrect orientations of organs

Question 41

Hox genes

Answer 41

A subset of homeobox genes arranged in a clusters on a chromosome, found in bilateral animals(existed in common ancestors), in some animal lineages e.g vertebrates. Hox genes have been duplicated resulting in multiple Hox clusters Correct positioning of body parts- head to tail (anterior to posterior) spatial (sequential head to tail) and temporal (time order head first) arrangement

Question 42

The layout of an organism

Answer 42

Body plans are represented as cross sections through tissue layers Diploblastic animals have two primary tissue layers, and triploblastic have three

Question 43

Animals are segmented

Answer 43

Common feature of animals is that they derive from segments. Segments have multiplied overtime and are specialised to perform various functions Hox genes in various segments derive their development and function- mouthparts in the head, limbs or wings in the thorax Hox genes drive the development

Question 44

Embryo development

Answer 44

Hox genes are activated and expressed in order along the anterior posterior axis Sequential and temporal- order of gene expressions corresponds to sequential and temporal development of body parts(collinearity) Hox genes encode homeodomain proteins- act in the nucleus as transcription factors These are regulated by gap genes and pair rule genes which are regulated by maternal mRNA

Question 45

Body shapes

Answer 45

Give Rise to planes of symmetry which depend on their body plans Radical symmetry- no left or right sides, just top and bottom (diploblasts) Bilateral symmetry- most animals have left to right sides and head and tail (triploblasts) Asymmetry- no lines of symmetry

Question 46

Mitosis

Answer 46

Zygote - embryo - adult Mitosis is regualted by homeobox and Hox genes Daughter cell contain full genome and clone of parents Differentiation- some genes are switched off (not expressed) Hayflic constant- normal body cells can be divided around 50 times

Question 47

Apoptosis

Answer 47

Programmed cell death -Occurs when cells have reached the hayflick limit -Timely and orderly -No other cells around will get damaged -Allows for pruning

Question 48

Ways for apoptosis to be signalled

Answer 48

-Cytokines from the immune system -Hormones -Growth factors -Nitric oxide (increases the permeability of the inner membrane of mitochondria All of these cause apoptosis inhibitor proteins to be themselves inhibited- thus allowing for the activation of the apoptotic pathways

Question 49

Stages of apoptosis

Answer 49

1. Enzymes break down the cell cytoskeleton 2. The cytoplasm condenses and organelles tightly pack 3. The plasma membrane changes and structures called ‘blebs’ form 4. Chromatin condenses and the nuclear envelope breaks- DNA fragments 5. The cell breaks into vesicles that are taken up by phagocytosis. These vesicles contain a signalling molecule called phosphotidylserine 6.the debris is disposed of and doesn’t damage any other cells around 7. The process is very quick

Question 50

Roles of apoptosis

Answer 50

Excess cells shrink and ultimately phagocytosed, the cellular components can then be reused No hydrolytic enzymes released into tissues During limb development digits separate from each other Removes ineffective or harmful t lymphocytes

Question 51

Rate of apoptosis

Answer 51

Children- between 20-30 billion cells a day undergo apoptosis Adults- 50-70 million apoptising cells The rate of dying is equal to the rate of mitosis Too much apoptosis: cell loss/degradation Too little apoptosis: tumours

Question 52

Genes that regulate cel cycle are also involved in body plan progression

Answer 52

Cyclins and cyclin dependant kinases govern (CDK)the process through the cell cycle The checkpoints within the cell cycle are their to prevent the damage of DNA -CDK- catalyse phosphorylation of certain target proteins which activates or inactivates them

Question 53

Mutations

Answer 53

Sickle cell traits- HnHs HsHs- sickle cell anaemia Hs increases the resistance to plasmodium falciparum ‘malaria’ Cystic fibrosis- one less amino acid- doesn’t allow for movement of chloride ions

Question 54

Healer cells

Answer 54

Used for cloning and polio vaccine

Question 55

Causes of phenotypic variation (observable characteristics)

Answer 55

Genetic factors Chromosome mutation Gene mutation Meiosis- crossing over in prophase 1 - independent assortment in metaphase 1 and 2 Random fertilisation

Question 56

Chlorosis example

Answer 56

Lack of light- switch off genes that produce chlorophyll Mineral deficiency- lack of iron or magnesium (required for enzymes which manufactor chlorophyll as its a co factor)

Question 57

Continuous variation

Answer 57

Any characteristics

Question 58

Discontinuous variation

Answer 58

A characteristic that can only appear in specific values. Mostly controlled by genes, and only 1-2 at a time

Question 59

Genotype

Answer 59

The allele combination of an individual is known as the genotype

Question 60

Phenotype

Answer 60

Physical features you can see in an organism is known as phenotype

Question 61

Dominant

Answer 61

A dominant allele is always expressed and masks the recessive

Question 62

Recessive

Answer 62

Need two of the recessive alleles for the trait to be expressed

Question 63

Homozygous

Answer 63

Both alleles are the same

Question 64

Heterozygous

Answer 64

Alleles are different

Question 65

Gregor Mendel

Answer 65

‘Father of genetics’ He studied genetics which can be masked in one generation but expressed in the next generation Completed the pea experiment (pod shape and colour)

Question 67

Law of particulate inheritance

Answer 67

Each gene is controlled by two factors (Each gene having two alleles) Factors do not blend but may be either recessive or dominant

Question 68

Genetic crosses

Answer 68

The offspring in genetic crosses are referred by how many generations removed they are from the parental generation F1- the heterozygous offspring of a cross between two true breeding parents F2- offspring of a cross between two F1 offspring

Question 69

Monohybrid cross

Answer 69

Examines the inheritance of one trait (flower colour in peas)

Question 70

Selfing

Answer 70

Some particular gene crosses wil reveal specific information about parental lines. These breeding tests are designed to reveal the genotype of parents (selfing/test crosses) Its only used in plants as its self fertilisation - they are fertilised with their own pollen, rather phenotypic ratios of the progeny indicate the likely parental genotype

Question 71

Test cross and back cross

Answer 71

An individual of a dominant phenotype may be homozygous dominant or heterozygous, test crosses it with a know breed of a recessive, this will reveal a definitive answer on the genotype of the unknown

Question 72

Dihydrid

Answer 72

Inheritance of more than 1 gene

Question 73

Things to remember when completing a dyhibrid cross

Answer 73

Fertilisation is random -Genes being studied are both on the same chromosome, and there is no crossing over occurring - -during meiosis then the genes are linked and will be inherited together These things describe why results are different from the expected results

Question 74

Co dominance

Answer 74

Both alleles in the heterozygotes contribute to the phenotype In cases of con dominance neither alleles dominates and the heterozygote is intermediate in phenotype between the two homozygotes

Question 76

Multiple alleles in blood

Answer 76

The three common blood groups of the human is ABO blood group system are determined by three alleles Ia Ib and Io, this is an example of a multiple allele system for a gene Any one individual possesses only two alleles and they can be expressed equally

Question 77

Sex determination

Answer 77

In most cases sex determination of an organism is controlled by the sex chromosomes provided by each parent Evolved to regulate ratios and preserve genetic differences. Humans are heterogametic sex- either X or Y chromosomes Males are not always heterogametic- for example birds and butterfly’s, simply just X whereas females are XX

Question 78

Sex linkage

Answer 78

Refers to the phenotypic expression of an allele that it depends on the sex of the individual and is directly tied to the sex chromosome Most sex linked genes are present on the X chromosome, and have no corresponding allele on the smaller male chromosome

Question 79

Haemophilia

Answer 79

X linked genetic illness Men either have it or they do not Females can carry this by they will not be affected b y the gene And their is no corresponding loci on the Y chromosome, men have to express the allele present on the X chromosome

Question 80

Autosomal linkage

Answer 80

The condition in which alleles lie close together on the same chromosome

Question 81

Recombinant offspring

Answer 81

Different allele combinations to their parents The closer the Genes are the less likely they are to be separated during crossing over, meaning that fewer recombinant offspring are produced Recombination frequency = number of recombinant offspring / total number of offspring

Question 82

What does the recombination frequency show

Answer 82

If 50% or more there is no linkage present- could be that genes are on different chromosomes Less than 50% means that they are linked and independent assortment has been hindered

Question 83

Epistatis

Answer 83

This is where the product of one gene directly effects a different allele- seen in characteristics where they are considered to be continuous Interaction between two or more genes for the same characteristic

Question 84

Antagonistic action

Answer 84

If the first allele is homozygous recessive for a gene it could prevent the expression of the gene in the second locus If the first gene is homozygous recessive its known as RECESSIVE epistasis - some epistatic mechanisms can have a dominant allele at the epistatic locus, its called DOMINANT epistasis

Question 85

Dominant epistasis

Answer 85

Is where the presence of one allele will over-ride the presence of a dominant allele in the second gene location E.g chickens, feather colour is determined by the dominant epistatic mechanism

Question 86

Evolution and factors effecting it

Answer 86

‘Evolution is the change in inherited characteristics overtime’ Natural selection; -Mutations- give rise to new alleles in the populations- genetic variation -Some alleles mean that an organism is better adapted to survive -Selection pressure -Some organisms are better adapted to survive and reproduce -Pass over alleles onto their offspring -Repeated over many generations- allele frequency changes over time

Question 87

Population genetics

Answer 87

Investigates how allele frequency change overtime Allele frequency is a figure and its expressed as a probability of a particular allele present in a population of organisms

Question 88

Gene pools

Answer 88

Is defined as the sum total of all the genes present in a population at any one time

Question 89

Biological species

Answer 89

A grouping of organisms that can interbreed and are reproductively isolated from other such groups (produce fertile offspring)

Question 90

Species are recognised by

Answer 90

Basis of their morphology (size, shape, appearance), and more recently by genetic analysis

Question 91

Population genetics

Answer 91

Comprises the total number of one species in a particular area, all members of the population have the opportunity to interact with each other (including breeding)

Question 92

Analysing a gene pool

Answer 92

Determining the frequency of allele types and genotypes, it is possible to determine the state of the gene pool (if it’s stable or undergoing change)

Question 93

The assumptions of the hardy- Weinberg equation

Answer 93

-No mutations -population large enough, so sample has neglegible error -No sexual selection -no genetic shift

Question 94

Hardy- Weinberg equilibrium

Answer 94

Population that shows no phenotypic change over many generations is said to be stable - genetic equilibrium of large sexually reproducing populations, frequency of alleles in a population will remain constant from one generation to the next

Question 95

The actual equation for hardy Weinberg

Answer 95

P squared + 2pq+ q squared =1 psquared is the homozygous dominant 2pq is geterozygous Q squared is homozygous recessive

Question 96

Population regulation

Answer 96

Population size is regulated by environmental factors that limit population growth, these may be dependant or independent of the population density

Question 97

Density independent factors

Answer 97

Abiotic Physical factors e.g rainfall Catastrophic events e.g flooding Regardless of the population density these are the same for all individuals.

Question 98

Density dependant factors

Answer 98

Biotic Food supply, disease, competition and predation. The effect of these factors are influenced by population density

Question 99

Causes of changes to allele frequency

Answer 99

Mutations Gene flow Genetic shift- loss of a phenotype from a population (failure to find a mate) Bottle necks- event , causes most of the population to be killed, only a small surviving population which interbreeds Founder effect- geographically isolated populations become a different species and cannot interbreed (will not produce fertile offspring

Question 100

Stabilising selection

Answer 100

Probably the ost common trend in natural populations, it favours the most common phenotype as the best adapted Reduces variation, selects against the extremes at both ends Results in a bell shaped curve which is narrower

Question 101

Human birth weight stabilising selection

Answer 101

Most births between 3-4Kg Histogram shows the percentage of births for each weight class, red line is for mortality Medical intervention has reduced this and increased survival.

Question 102

Directional selections

Answer 102

Usually due to an environmental change Favours one extreme of the phenotypic range

Question 103

Disruptive selection

Answer 103

Favours phenotypes at both extremes and eliminates the intermediate variants (becomes two peaks) Can lead to polymorphism- same population starts to looks slightly different to each other May occur due to changes in the environment

Question 104

What is speciation

Answer 104

Formation of a new species though the process of evolution No gene flow between the new group and the original group Alleles continue to undergo mutations And they come reproductively isolated after many generations Making them a new species

Question 105

Geographical isolation

Answer 105

Allopathic speciation Georgraphical barrier- population is isolated- mutation, gene drift, natural selection- reproductive barriers arise/ reproductive isolation- new species

Question 106

Reproductively isolated

Answer 106

Sympatric speciation Without a geographical barrier e.g different eating patterns (behaviour difference) usually occur in plants

Question 107

Artificial selection

Answer 107

Humans have control of the breeding of domesticated animals and plants for centuries Breeding individuals for the most desirable phenotypes, can cause a range of phenotypic variation over short periods of time

Question 108

Problems with artificial breeding

Answer 108

Genetic problems Vulnerability to disease (present in all members of the species) Lead to interbreeding Heart defects in larger dogs

Question 109

Gene and seed banks

Answer 109

Act as a genetic resource Seed banks keep sends from domentistacted and wild species They store sperm and eggs from a wide variety of organisms