Inheritance, Variation And Evolution Flashcards
(257 cards)
1
Q
What is sexual reproduction?
A
Type of reproduction.
Involves the production of gametes by meiosis.
A gamete from each parent fuses to form a zygote.
Genetic information from each gamete is mixed so the resulting zygote is unique.
2
Q
What are gamates?
A
Sex cells
Haploid
3
Q
What is meiosis?
A
Form of cell division involved in the formation of gamates in reproductive organs
Chromosome number is halved
Involves two divisions
4
Q
What must occur prior to meiosis?
A
Interphase - copies of genetic information are made during this process
5
Q
What happens during the first stage of meiosis?
A
Chromosome pairs line up along the cell equator
The pair of chromosomes are separated and move to opposite poles of the cell
Chromosome number is halved
6
Q
What happens during the second stage of meiosis?
A
Chromosomes line up along the cell equator.
The chromatids are separated and move to opposite poles of the cell.
Four unique haploid gametes are produced.
7
Q
Why is meiosis important for sexual reproduction?
A
It increases genetic variation.
It ensures that the zygote formed at fertilisation is diploid.
8
Q
Describe fertilisation and its resulting outcome
A
Gametes join together to restore the normal number of chromosomes and the new cell then divides by mitosis. As the embryo develops, cells differentiate.
9
Q
What are the advantages of sexual reproduction?
A
It creates genetic variation in offspring
Natural selection can be speeded up by humans in selective breeding
10
Q
What is asexual reproduction?
A
Type of reproduction.
Involves mitosis only.
Produces genetically identical offspring known as daughter cells.
11
Q
Describe the advantages of asexual reproduction
A
Only one parent is required.
Lots of offspring can be produced in a short period of time
Requires less energy and time as do not need a mate.
12
Q
What are the disadvantages of asexual reproduction?
A
No genetic variation reducing the probability of a species being able to adapt to environmental change
13
Q
Describe the circumstances in which Malarial parasites reproduce sexually and asexually
A
Sexual reproduction in the mosquito. Asexual reproduction in the human host.
14
Q
Describe the circumstances in which fungi reproduce sexually and asexually
A
Asexual reproduction by spores.
Sexual reproduction to give variation.
15
Q
Describe the circumstances in which plants reproduce sexually and asexually
A
Sexual reproduction to produce seeds.
Asexual reproduction by runners or bulb division
16
Q
What is DNA?
A
A double-stranded polymer of nucleotides, wound to form a double helix
The genetic material of the cell found in its nucleus
17
Q
What is genome?
A
The entire genetic material of an organism
18
Q
Why is understanding the human genome important?
A
● Searching for genes linked to different types of disease.
● Understanding and treating inherited disorders.
● Tracing human migration patterns from the past.
19
Q
What is a chromosome?
A
a long continuous thread of DNA that carries genetic information in the form of genes
20
Q
How many chromosomes do human body cells have?
A
46 chromosomes (23 pairs)
21
Q
How many chromosomes do humans gametes have?
A
23 chromosomes
22
Q
What is a gene?
A
A small section of DNA that codes for a specific sequence of amino acids which undergo polymerisation to form a protein
23
Q
What are the monomers of DNA?
A
nucleotides
24
Q
What are DNA nucleotides made of?
A
Common sugar
Phosphate group
One of four bases: A, T, C or G
25
What are the four bases found in nucleotide?
Adenine, Thymine, Cytosine and Guaunine
26
Describe how nucleotides interact to form a molecule of DNA
Sugar and phosphate molecules join to form a sugar-phosphate backbone in each DNA strand
Base connected to each sugar
Complementary base pairs (A pairs with T, C pairs with G) joined by weak hydrogen bonds
27
Explain how a gene codes for a protein
A sequence of three bases in a gene forms a triplet
Each triplet codes for an amino acid
The order of amino acids determines the structure (i.e. how it will fold) and function of protein formed
28
Why is the 'folding' of amino acids important in proteins such as enzymes?
The folding of amino acids determines the shape of the active site which must be highly specific to the shape of its substrate.
29
What is protein synthesis?
The formation of the protein from a gene
30
What are the two stages of protein synthesis?
transcription and translation
31
What does transcription involve?
The formation of mRNA from a DNA template
32
Outline transcription
1. DNA double helix unwinds
2. RNA polymerase binds to a specific base sequence of non-coding DNA in front of a gene and moves along the DNA strand
3. RNA polymerase joins free RNA nucleotides to complementary bases on the coding DNA strand
4. mRNA formation complete. mRNA detaches and leaves the nucleus.
33
What does translation involve?
A ribosome joins amino acids in a specific order dictated by mRNA to form a protein.
34
outline translation
1. mRNA attaches to a ribosome.
2. Ribosome reads the mRNA bases in triplets. Each triplet codes
for one amino acid which is brought to the ribosome by a tRNA
molecule (carrier molecule).
3. A polypeptide chain is formed from the sequence of amino
acids which join together.
35
What is a mutation?
A random change in the base sequence of DNA which results mostly in no change to the protein code for, or genetic variation of the protein (slight alteration but appearances and function remains)
Mutations occur continuously
36
Describe the effect of gene mutation in coding DNA
If a mutation changes the amino acid sequence, protein structure and function may change (an enzyme may no longer fit its substrate binding site or a structural protein may lose its strength).
If a mutation does not change amino acid sequence, there is no effect on protein structure or function.
37
What is non-coding DNA?
DNA which does not code for a protein but instead controls gene expression
38
Describe the effect of gene mutation in non-coding DNA
Gene expression may be altered, affecting protein production and the resulting phenotype.
39
What are alleles?
different versions of the same gene
40
What is a dominant allele?
A version of a gene where only one copy is needed for it to be expressed
41
What is a recessive allele?
A version of a gene where two copies are needed for it to be expressed
42
What is meant when an organism is homozygous?
When an organism has two copies of the same allele (two recessive or two dominant).
43
What is meant when an organism is heterozygous?
When an organism has two different versions of the same gene (one dominant and one recessive).
44
What is the genotype?
The genes present for a trait
45
What is phenotype?
physical (visible) characteristics
46
How are dominant alleles represented in the punnet square?
They are represented using uppercase letters.
47
How are recessive alleles represented?
They use the lower case version of the same letter as the dominant allele
48
What is the problem with single gene crosses?
Most characteristics are controlled by multiple alleles rather than just one
49
What is an inherited disorder?
A disorder caused by the inheritance of certain alleles.
50
Give 2 examples of inherited disorders
● Polydactyly (having extra fingers or toes) - caused by a dominant allele.
● Cystic fibrosis (a disorder of cell membranes) - caused by a recessive allele.
51
How are embryos screened for inherited disorders?
During IVF, one cell is removed (from an 8 cell embryo) and tested for disorder-causing alleles. If the cell doesn't have any indicator alleles, then the originating embryo is implanted into the uterus.
52
What are ethical issues concerning embryo screening?
It could lead to beliefs in society that being disabled or having a disorder is less human or associated with inferiority.
The destruction of embryos with inherited disorders is seen by some as murder as these would go on to become human beings.
It could be viewed as part of the concept of designer babies as it may be for the parents convenience or wishes rather than the child's wellbeing.
53
What are the economic issues concerning embryos screening?
Cost of hospital treatment and medication will need to be considered if it is known that a child will have an inherited disorder and financial support explored I'd necessary
54
What are the social issues concerning embryos screening?
Social care for children with inherited disorders may need to be considered if parents are unable to provide care
If an embryo is found to have an inherited disorder and is terminated, this can prevent a child and its parents from potential suffering in the future due to the disorder
55
What is gene therapy?
The insertion of a normal allele into the cells of a person with an inherited disorder to functionally replace the faulty allele.
56
What are ethical concerning gene therapy?
Some people believe that it is going against and 'playing God'.
The introduced genes could enter sex cells and so be passed to future generations.
57
What are sex chromosomes?
A pair of chromosomes that determine sex:
● Males have an X and a Y chromosome
● Females have two X chromosomes
58
Why does the inheritance of a Y chromosome mean that an embryo develops into a male?
Testes development in an embryo is stimulated by a gene present on the Y chromosome
59
What is a sex-linked characteristics?
A characteristic that is coded for by an allele found on a sex chromosome
60
Why are the majority of genes found on the X chromosome rather than the Y chromosome?
The X chromosome is bigger than the Y chromosome so more genes are carried on it.
61
why are men more likely to show sex-linked recessive traits than women?
Many genes are found on the X chromosome that have no counterpart on the Y chromosome
Women (XX) have two alleles for each sex-linked gene whereas men (XY) often have one allele, only one recessive allele is required to produce the recessive phenotype in males
62
What is variation?
Differences in the characteristics of individuals in a population
63
What is causes of variation within a species?
Genetics and environmental
64
What is genetic variation?
Variations in the genotypes of organisms of the same species due to the presence of different alleles
Creates differences in phenotypes
65
What creates genetic variation in a species?
Spontaneous mutations
Sexual reproduction
66
State the three types of gene mutation
insertion, deletion, substitution
67
How may a gene mutation affect an organism's phenotype?
Neutral mutation does not change the sequence of amino acids. Protein structure and function same. No effect on phenotype.
Mutation may cause a minor change in an organism's phenotype e.g. change in eye colour.
Mutation may completely change the sequence of amino acids. This may result in a non-functional protein. Severe changes to phenotype.
68
What is the consequence of a new phenotype caused by a mutation being suited to an environmental change?
There will be a rapid change in the species.
69
What is evolution?
The gradual change in the inherited characteristics of a population over time (occurs due to natural selection which may result in the function of a new species)
70
Outline the theory of natural selection
All species of living things have evolved from simple life forms that first developed more than 3 billion years ago.
1. Genetic variation exists due to spontaneous mutations.
2. Selection pressures (e.g. competition, disease) exist.
3. Random mutation gives an organism a selective advantage.
4. Organism is better adapted to the environment and survives.
5. Organism reproduces, passing on its beneficial alleles.
6. Frequency of advantageous alleles increase.
71
How do two populations become different species?
When their phenotypes become different to the extent that they can no longer interbreed to produce fertile offspring.
72
What is selective breeding?
The process by which humans artificially select organisms with desirable characteristics and breed them to produce offspring with similar phenotypes
73
Outline the main steps involved in selective breeding
1. Identify a desired characteristic e.g. disease resistance
2. Select parent organisms that show the desired traits and breed them together
3. Select offspring with the desired traits and breed them together
4. Process repeated until all offspring have the desired traits
74
Give examples of characteristics selected for in selective breeding
Disease resistance in crops
Higher milk or meat production in animals
Gentle nature in domestic dogs
Large flowers
75
What is the main advantage of selective breeding?
Creates organisms with desirable features:
● Crops produce a higher yield of grain
● Cows produce a greater supply of milk
● Plants produce larger fruit
● Domesticated animals
76
Other than in agriculture, where else is selective breeding useful?
In medical research
In sports e.g. horse racing
77
Outline the disadvantages of selective breeding
Reduction in the gene pool which becomes especially harmful if sudden environmental change occurs
Inbreeding results in genetic disorders.
Development of other physical problems
Potential to unknowingly select harmful recessive alleles.
78
What is genetic engineering?
The modification of the genome of an organism by the insertion of a desired gene from another organism - genes from chromosomes of humans and other organisms can be 'cut out' and transferred to cells of other organisms.
79
Give an example of uses for genetically modified plants
Disease resistance
Produce larger fruits
80
What is the use for genetically modified bacteria cells?
To produce human insulin to treat diabetes mellitus.
81
Describe the benefits of genetic engineering
Increased crop yields for growing population
Useful in medicine
GM crops produce scarce resources
82
Describe the risks of genetic engineering
- Long-term effects of consumption of GM crops unknown
- Negative environmental impacts
- Late-onset health problems in GM animals
- GM seeds are expensive. LEDCs may be unable to afford them or may become dependent on businesses that sell them.
83
What is the name for crops that have had their genetic modified?
Genetically modified (GM) crops
84
What is Bacillus thuringiensis?
A microbial sprayable bacterial spore that paraylzes the gut causing death.
85
How is genetic engineering used to protect crops against insects?
The gene for toxin production in Bt can be isolated and inserted into the DNA of crops.
Bt crops now secrete the toxin which kills any insect larvae that feed on it.
86
What are the benefits of Bt crops?
Increased crop yields (fewer crops damaged).
Lessens the need for artificial insecticides.
Bt toxin is specific to certain insect larvae so is not harmful to other organisms that ingest it.
87
What are the risks of Bt crops?
Long term effects of consumption of Bt crops unknown.
Insect larvae may become resistant to the Bt toxin.
Killing insect larvae reduces biodiversity.
88
Describe the process of genetic engineering
1. DNA is cut at specific base sequences by restriction enzymes to create sticky ends.
2. Vector DNA cut using the same restriction enzymes to create complementary sticky ends.
3. Ligase enzymes join the sticky ends of the DNA and vector DNA forming recombinant DNA.
4. Recombinant DNA mixed with and taken up by target cells
89
What is a vector?
A structure that delivers the desired gene into the recipient cell
90
How can plants be cloned?
Taking plant cuttings
Tissue culture
91
What is tissue culture?
Using small groups of cells from part of a plant to grow identical new plants.
92
Describe how plants are grown using tissue culture?
1. Select a plant that shows desired characteristics
2. Cut multiple small sample pieces from meristem tissue
3. Grow in a petri dish containing growth medium
4. Transfer to compost for further growth
93
What must be ensured when preparing tissue cultures?
Ensure aseptic conditions to prevent contamination by microorganisms
94
What does the growth medium contain?
Nutrients and growth hormones
95
What are the advantages of growing plants by tissue culture?
Fast and simple process.
Requires little space.
Enables the growth of many plant clones with the same desirable characteristics.
Useful in the preservation of endangered plant species
96
What are the disadvantages of growing plants by tissue culture?
- Reduction in the gene pool
- Plant clones often have a low survival rate
- Could unknowingly increase the presence of harmful recessive alleles
97
Describe the plant cutting method of plant cloning
Older but simpler method than tissue culture
Gardeners use this method to produce many identical new plants from a parent cell
98
Detail the process of the plant cuttings method of plant cloning
1. A branch is cut off from the parent plant.
2. The lower leaves of the branch are removed and the stem is
planted.
3. Plant hormones are used to encourage new root development.
4. A plastic bag is used to cover the new plant to keep it warm and
moist.
5. New roots and a new plant is formed after a few weeks.
99
What does embryo transplanting involve?
Pre-specialised cells from a developing animal embryo are split apart.
The resulting separate but identical embryos are transplanted into host mothers.
100
Describe how adult cell cloning is performed
1. The nucleus is removed from an unfertilised egg cell.
2. The nucleus from an adult body cell, such as a skin cell, is inserted into the egg cell.
3. An electric shock stimulates the nucleated egg cell to divide and it forms an embryo.
4. The embryo cells contain the same genetic information as the adult body cell.
5. When the embryo is a ball of cells, it is inserted into the uterus of an adult female to continue de
101
Outline the theory of evolution by natural selection
Individuals of a species show a wide range of variation for a characteristic. Those with the characteristic most suited to the environment will survive breed most successfully. The desirable characteristic that has enabled the individuals to survive are passed onto their offspring.
102
Why was Darwin's theory of evolution not accepted initially?
Most people believed in creationism
Insufficient evidence to prove the theory
The mechanism of variation and inheritance was not known at that time
103
What was Jean-Baptiste Lamarck's theory of inheritance?
That changes during the lifetime of an organism can be inherited.
104
What is speciation?
the formation of new and distinct species in the course of evolution
when two populations become so varied that they cannot interbreed to produce fertile offspring
105
What is the definition of a species?
a group of living organisms consisting of similar individuals capable of exchanging genes or interbreeding.
106
Outline the process of speciation through geographic isolation
Two populations of the same species are separated geographically
Geographic isolation prevents interbreeding and mixing of genes between the populations.
Due to different selection pressures, different mutations occur producing different phenotypes in each population.
Over time, the two populations may evolve so that they are not able to interbreed.
107
Why is genetic variation important in speciation?
Genetic variation produces phenotypic variation, some of which are better suited to the environment and are selected for.
108
How did Mendel study inheritance?
Through carry breeding experiments on plants and analysing the ratio of characteristics in offspring.
109
Why was Mendel's work not recognised until after his death?
He couldn't explain the mechanism of inheritance, as chromosomes were only discovered after his death
It was not communicated well to other scientists and not published in a reputable scientific journal
110
State two kinds of evidence used to show evolution.
Fossils and antibiotic resistance in bacteria
111
How are fossils formed?
Parts of organisms that have not decayed due to conditions needed for decay being absent.
Parts of organisms that have been replaced by minerals as they decayed eg. bones.
Traces of organisms are preserved, covered in sediment and becoming rock.
112
Why are there few traces of early life-forms left behind?
They are mostly soft-bodied.
113
How do fossil acts as evidence for evolution?
Scientist can identify the ages of the fossils and use them to show how organisms change over time
114
What do branches in evolutionary trees indicate?
Where speciation has occurred.
115
What is extinction?
Where there are no individuals of a species still alive.
116
State the factors that may lead to extinction
New disease, predation, competition, changes in the environment and catastrophic events
117
What enables bacteria to evolve quickly?
The fast rate of their reproduction.
118
Outline the process of antibiotic resistance bacteria evolving
Mutations occur in bacteria producing genetic variation.
Certain strains are resistant to antibiotics and are not killed when the antibiotic is applied.
Resistant strains survive and reproduce.
Over time, the population of the resistant
119
Why are resistant strains of bacteria dangerous?
People have no immunity to them and there is no effective treatment.
120
State an example of resistance strain of bacteria
MRSA
121
Why is it difficult to keep up with emerging resistance strains?
Developing antibiotics have a high cost and take a long time to develop.
122
What are the classes of organisms as determined by Carl Linnaeus?
Kingdom, Phylum, Class, Order, Family, Genus, Species
123
Which features are living creatures traditionally classified by?
By their structure and characteristics.
124
What is the binomial system of naming organisms?
Genus name followed by species name
125
Why were new classification models proposed?
Developments in microscopy allowed better examination of internal structures.
Improvement in understanding of biochemical processes.
126
State the three domains
Archaea, Eukarya, Bacteria
127
How are evolutionary trees created?
By examining the DNA of different species and analysing how similar the sequences are.
128
Describe the disadvantages of sexual reproduction
Two parents are required. This makes reproduction difficult in endangered populations or in species which exhibit solitary lifestyles
More time and energy is required so fewer offspring are produced
129
What is genetic disorder?
A disease caused by errors in a DNA sequence, disorders are heritable so can potentially be passed on to offspring
130
What is cystic fibrosis?
A genetic disorder of the cell membranes that leads to excess mucus that damages organ systems, caused by a recessive allele
131
What is the inheritance of cystic fibrosis?
Cystic fibrosis is a recessive disorder that will only occur if two recessive alleles are present, heterozygous individuals are carriers
132
What is a carrier?
An individual who carries a recessive allele for a disorder but does not express the disorder's phenotype
133
What is polydactyl?
A genetic disorder where individuals have extra fingers or toes, caused by a dominant allele
134
What is the inheritance of polydactyly?
Polydactyly is a dominant disorder so it only takes one allele for the disorder to occur, it is impossible to be a carrier for polydactyly
135
What is embryo screening?
The extraction of a cell from an embryo made by IVF which can be analysed to identify any genes that link to genetic disorders
136
What are gamete cells?
Reproductive cells that contain 23 chromosomes, half the number of chromosomes in a human body cell
137
What is the inheritance of chromosomes?
Organisms inherit one copy of each chromosome from their mother and one copy of each chromosome from their father
138
What is the sequence of the three bases?
The genetic code for an amino acid also called a codon or triplet, this arrangement of three bases leads to the formation of one specific amino acid
139
What are the types of mutation?
Base substitution, insertion, deletion or inversion
140
What is base insertion or deletion?
Where a single base is added or removed in a DNA sequence, which could lead to the translation of a different amino acid
141
What is base substitution or inversion?
Where a single base is swapped or where the order of several bases change, which could lead to the translation of a different amino acid
142
What are the insignificant effect of mutations?
Most mutations have no effect on the shape of the protein and even if the shape changes slightly it may not affect the protein's function
143
What are the significant effects of mutations?
Mutations can have a significant effect in rare cases, an altered enzyme may not fit a binding substrate or an altered structural protein may lose its strength
144
What is the effect of genetic variant on non-coding DNA?
Altering the sequence of non-coding DNA could result in genes that are typically off being switched on or vice versa
145
What is the complementary base pairs?
The bases found on one strand of DNA must pair with specific bases on the other DNA strand, so that the strands can be held together
146
What is the complementary strand of C?
A base that is complementary to G, it will not pair up with A or T on the complementary strand
147
What is the complementary strand of A?
A base that is complementary to T, it will not pair up with a C or G on the complementary strand
148
What is the sugar in DNA?
Also called deoxyribose sugar, the sugar joins with a nitrogenous base and a phosphate group to make a nucleotide
149
What is the phosphate group?
Makes up the backbone of the DNA structure by joining with the sugar group in an alternating sequence
150
What is the sugar-phosphate backbone?
An important structural component of the DNA strands, made up of alternating sugar and phosphate sections
151
What is genetic material?
The general term for the material used to store genetic information in a cell
152
What is human genome project?
A genetic research project that started in 1990 and completed in 2003, that successfully mapped and sequence the entire human genome
153
What is treating diseases?
Understanding the human genome has helped medical professionals identify individuals who may be more susceptible to specific diseases
154
What are genealogical DNA tests?
A DNA-based test that looks at specific regions of an individual's genome to determine the individual's ancestry and ethnic heritage
155
What are migration patterns?
Genetic markers can be used to map migration patterns by comparing the DNA of different populations or by looking at ancestral fossil DNA
156
What is genetic markers?
Specific regions of the human genome such as the Y chromosome and mitochondrial DNA that can be used to study genealogy
157
What is genealogy?
The study of family, family history and the tracing of ancestral lineages
158
What are the advantages of sexual reproduction?
Produces variation, variation provides a survival advantage by natural selection, selective breeding can be used to increase food production
159
What is natural selection?
If an environment changes, variation can allow for natural selection where the fittest individuals are more likely to reproduce
160
What are the favourable conditions of asexual reproduction?
Asexual reproduction typically occurs when environmental conditions are favourable, so many identical offspring can quickly be produced
161
What is the susceptible to environmental change in asexual reproduction?
Asexual organisms lack variation, meaning an entire population could be wiped out by a disease or sudden environmental change
162
What is an identical offspring?
The result of asexual reproduction where the process of mitosis leads to genetically identical individuals or clones
163
What is non-identical offspring?
The result of sexual reproduction where the process of meiosis leads to individuals with genetic variations
164
What is the purpose of meiosis?
To shuffle genetic information leading to variation and to produce cells that will combine to make a cell with the correct number of chromosomes
165
What is genetic reshuffling?
Genetic information is swapped between chromosome pairs during meiosis, resulting in gametes with variation
166
What the cell division after fertilisation?
Following the fusion of gametes, a fertilised egg divides by mitosis and begins to rapidly increase in cell number
167
What is gonads?
The reproductive organs that produce gametes via meiosis, such as the testis or ovary
168
When does mitosis occur?
During asexual reproduction or the growth and repair of an organism's tissues, by producing new body cells
169
What is a body cell?
A typical cell with two complete copies of each chromosome, that is not involved in reproduction
170
What are the features of meiosis?
Two stages of division, four non-identical daughter cells produced, 23 chromosomes in each haploid cell, needed for sexual reproduction, occurs in gonads
171
What are the features of mitosis?
One stage of division, two identical daughter cells produced, 46 chromosomes in each diploid cell, involved in asexual reproduction, can occur in body tissue
172
What is plant cuttings?
An older method used by gardeners to produce many identical new plants from a parent plant
173
What are embryo transplants?
Splitting cells apart from a developing animal embryo before they become specialised, then transplanting the identical embryos into host mothers
174
What are adult cell cloning?
A method of cloning that involves combining an unfertilised egg cell with the nucleus of an adult body cell, using electrical stimulation
175
What is nucleus extraction?
The first stage of adult cell cloning is to remove the nucleus from a donor organism's unfertilised egg cell
176
What is donor organism?
Unfertilised egg cells are harvested from an organism of the same or similar species as the desired organism to be cloned
177
What is enucleated egg cell?
An unfertilised egg cell without a nucleus
178
What is body cell nucleus transfer?
The nucleus of an adult body cell is extracted from the desired organism to be cloned and is later inserted into the enucleated egg cell
179
What is an adult body cell?
A differentiated cell from an adult organism such as a skin cell or nerve cell, that is not involved in reproduction
180
What is the electric shock stage?
Following the fusion of the body cell nucleus and enucleated egg cell, an electric shock stimulates the egg cell to divide to form an embryo
181
What are the products of adult cell cloning?
The embryo cells that have been electrically shocked now contain the same genetic information as the original adult body cell, the embryo is officially a clone
182
What is embryo development?
When the cloned embryo has developed into a ball of cells it is inserted into the womb of an adult female to continue development
183
What are the advantages of cloning?
Can be used to produce many organisms, can help achieve food security, can conserve endangered species and can potentially be used to bring species back from extinction
184
What are the disadvantages of cloning?
If many organisms are cloned they would be susceptible to the same diseases, low success rates, risk of complications, considered unethical and could be prone to misuse
185
What is genetically modified organism (GMO)?
An organism that has had its genetic information or genes manipulated, usually by genetic engineering
186
What is genetic engineering in plants?
Plant crops have been genetically engineered to be resistant to diseases or produce bigger and better fruits
187
What is making insect-resistant plants?
A gene responsible for making a toxin that kills insects is isolated from a ground-dwelling bacterium and is inserted into plants, using vectors
188
What is genetic engineering in bacteria cells?
Bacterial cells have been genetically engineered to produce useful substances such as human insulin to treat diabetes
189
What is making insulin?
A gene responsible for making insulin is isolated from cells of the human pancreas and is inserted via vectors into bacteria that can rapidly reproduce
190
What is the use of enzymes in genetic engineering?
Enzymes are used to isolate a required gene from an organism with a desirable characteristic
191
What is the use of vectors in genetic engineering?
The isolated required gene is inserted into a vector, which is then used to insert the gene into the required cells
192
What is bacterial plasmid?
A small ring of extra DNA found in bacterial cells, plasmids are cut open with enzymes and an isolated gene is inserted into them
193
What is gene transferal?
Genes are transferred to the cells of animals, plants or microorganisms at an early stage of development so they can develop with desired characteristics
194
What is a target organism?
The organism that is intended to be genetically modified, following the insertion of an isolated gene that codes for a desirable trait
195
What are the origins of selective breeding?
Humans have been selectively breeding organisms for thousands of years since they first bred food crops from wild plants and domesticated animals
196
What is selective breeding in plants?
Weeds have been selectively bred to make crops such as maize for corn, the wild mustard plant has been bred to make broccoli, kale and sprouts
197
What is selective breeding in domesticated animals?
Cattle and poultry have been selectively bred to be larger and produce more meat, dogs have been bred from wolf ancestors to be gentle or to have puppy-like features
198
What is inbreeding?
A consequence of selective breeding where some breeds are particularly prone to disease, deformities or inherited defects
199
What are some examples of continuous variation?
An organism's height or weight are examples of continuous variation as they can have any numerical value including all decimal numbers
200
What are some examples of discontinuous variation?
An animal's fur colour or a human's blood type or shoe size are examples of discontinuous variation as the data is best organised into distinct categories
201
What are the sources of variation?
All variants arise from mutations, most of which have no effect on the phenotype, some influence the phenotype and very few actually determine the phenotype
202
What is the genetic reshuffling during meiosis?
Genetic information is swapped between chromosomes during meiosis, which can be another source of variation other than mutations
203
What are the causes of variation?
Expression of genes that have been inherited, the conditions in which an organism has developed or a combination of genes and the environment
204
What are some examples of variation caused by genetic factors?
Blood type, skin or fur colour at birth, eye colour, genetic disorders
205
What are some examples of variation caused by the environment?
Scars, language or human modifications such as tattoos or piercings
206
What are the examples of genetic and environmental variation?
Weight, height, skin colour, hair colour
207
What is the frequency of mutation?
Mutations occur continuously but will very rarely lead to a new phenotype
208
What is the adaptive phenotypes?
If a new phenotype is suited to environmental change it can lead to a relatively rapid change in a species
209
What is survival of the fittest?
A concept of natural selection, where individuals with adaptive phenotypes are more likely to survive and pass on their genes to their offspring
210
What is competition?
Organisms that are less-well suited to their environments will need to use more effort to compete and survive, these less adapted organisms are more likely to die without reproducing
211
What are the causes of extinction?
Organisms unable to compete are at risk of extinction, where other organisms are better able to exploit the resources needed to survive
212
What are the factors leading to extinction?
Fewer available mates, lack of resources such as food and water, predation or poaching by humans, competition with other species, environmental change, disease, catastrophic events
213
What is conservation?
The efforts of humanity to try to preserve endangered or vulnerable species and protect them from extinction
214
What is mass extinction?
The sudden extinction of many organisms that is caused by a catastrophic event such as volcanic activity, extreme global temperature change or asteroid impact
215
What is antibiotic resistance?
Antibiotic-resistant bacterial strains are more likely to survive and reproduce when exposed to antibiotics, where other bacteria will die and leave many resources unexploited
216
What is antimicrobial resistance?
Microbes other than bacteria have also been identified as being resistant to specific drug treatments
217
What are the causes of antibiotic resistance?
When exposed to antibiotics the majority of a bacterial population will be destroyed, however some individuals may survive and undergo mutations that can make them resistant to antibiotics
218
What is MRSA?
A bacterial strain that is resistant to antibiotics and is prevalent in hospitals where it is very difficult to treat
219
How do you reduce the rate of antibiotic resistance?
Doctors should not prescribe antibiotics inappropriately, patients should complete any courses of antibiotics to prevent mutations, farms should not use antibiotics on livestock
220
What are new antibiotics?
The development of new antibiotics is costly and slow, it is unlikely to keep up with the emergence of new resistant strains
221
How can fossils be formed?
From parts of organisms that have not decayed, when parts of organisms are replaced by minerals, as trace fossils
222
What are the traces of fossils?
Footprints, burrows, shell impressions, rootlet traces that are preserved as fossils
223
What are the issues with the fossil record?
Not all organisms will fossilise and many early forms of life were soft-bodied, so very few traces of these organisms have been left behind
224
What is the difficulty of determining the origins of life?
Geological activity has destroyed most traces of early life forms, making it difficult for scientists to be certain how life began on Earth
225
What is the interpreting we can make of the fossil record?
We can learn from fossils how much or how little organisms have changed as life developed on Earth
226
What is fossil evidence?
Fossils have been found that are very similar to existing organisms, suggesting modern organisms may have evolved from or share a common ancestor with these ancient organisms
227
What are evolutionary trees?
A branched diagram that represents the relationship between many living and extinct organisms based on physical and genetic characteristics
228
What is antibiotic resistance in bacteria?
Resistant bacteria display evidence for evolution, where some bacteria have undergone mutations making them better adapted to surviving in antibiotic conditions
229
What is artificial selection?
Natural selection can be sped up in organisms via selective breeding, as demonstrated by Darwin who bred many fancy pigeons with very different characteristics
230
What is gene evidence?
An increased understanding of genetics provides support for evolution as it has been shown that characteristics are passed on to offspring in genes
231
What is the theory of evolution by natural selection?
A now widely accepted theory that has been supported by evidence, the theory suggests organisms can change over time due to natural selection
232
What are Mendel’s findings?
Mendel noticed that the inheritance of each characteristic is determined by units that are passed on to descendants unchanged
233
What is the importance of Mendel’s work?
Mendel didn't know at the time that the units he described were actually genes, his work expanded the knowledge of genetic inheritance before DNA was even discovered
234
What is Mendelian inheritance?
A type of biological inheritance that follows the principles proposed by Mendel, where the expression of a single trait is the result of the interaction of two alleles
235
What is blended inheritance?
At the time of Mendel's work many scientists believed that characteristics were simply blended when they were inherited
236
What are the reasons why Mendel's work was not originally accepted?
Mendel could not explain the science of inheritance, scientists did not understand his work and his work was published in an obscure and inaccessible journal
237
Who is Charles Darwin?
The famous naturalist who proposed the theory of evolution by natural selection, as a result of years of observations and research
238
What was the HMS beagle?
The ship used by Charles Darwin on his voyages around the world, Darwin made some very important observations on his round the world expedition
239
What was the Galapagos Islands?
A cluster of islands in the Pacific Ocean, Darwin observed a number of unique species that had adapted to each island such as the Galapagos finches and tortoises
240
What was the warning colouration?
A number of species can deter predators by displaying colours and patterns to suggest they are dangerous
241
What is mimicry?
Many species can display false warning colouration where they pretend to be another species that is poisonous, venomous or otherwise threatening
242
What are the classification systems?
Systems that are used to categorise organisms based on physical characteristics, relationships with other organisms, common ancestry, biochemical composition or genetics
243
What was the order of classification in the Linnaean system?
Kingdom, phylum, class, order, family, genus, species
244
What is a kingdom?
The first division of living things in a traditional classification system consisting of animal, plant, fungi, protist and prokaryote kingdoms
245
What is a phylum?
The second division of classified living things, examples include chordates or arthropods
246
What is a class?
The third division of classified living things, examples include mammals, birds, amphibians, fish and reptiles
247
What is an order?
The fourth division of classified living things, examples include carnivores or primates
248
What is a family?
The fifth division of classified living things, examples include canines and felines
249
What is a genus?
The sixth division of classified living things, examples include Felis and Panthera
250
What is a species?
The final division of classified living things, the species name is the combination of the genus and species division
251
What is a binomial system?
The universal scientific name of an organism that is based on the combination of its genus and species name, such as Homo sapiens
252
What are the scientific names in the classification system?
Most divisions of the classification system are not written in English, they are usually based on Latin or Greek terms
253
What is the development to classification systems?
New models of classification systems have been proposed as a result of microscopic improvements, improved structural understanding and knowledge of biochemical processes
254
What is the three-domain system?
A modern classification system with three branches containing eukaryotes, true bacteria and primitive bacteria
255
What is archaea?
Primitive bacteria that are found in extreme conditions such as hydrothermal vents or acid pools
256
What is bacteria?
Organisms that are classified as true bacteria
257
What is eukaryota?
Eukaryotes including protists, fungi, animals and plants
