AQA A-Level Biology Paper 2
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1. Alleles that are neither dominant nor recessive to Codominant
one another, so both alleles are always expressed
in the phenotype.
2. The inheritance of a single gene Monohybrid inheritance
3. Physical, behavioural, biochemical expression of an Phenotype
organisms genotype
4. The type of genes an individual has Genotype
5. Alles that is always expressed in the phenotype Dominant
6. Only expressed in the phenotype when homozy- Recessive
gous
7. both alleles are the same Homozygous
8. Both alleles for a specific gene are different Heterozygous
9. Position of a gene on a chromosome Loci
10. A set of instructions for a specific polypeptide Gene
11. Different forms of a gene Allele
12. 1. Expected ratios are probability Suggest four reasons why ob-
2. Sexual reproduction is random due to random served ratios are not the same
fusion of gametes and random assortment homol- as expected ratios (4).
ogous chromosomes.
3. Small sample size
4. Linked genes
13. 1. Homologous chromosomes pair up Meiosis results in cells that
2. Crossing over / chiasmata form; have the haploid number of
, AQA A-Level Biology Paper 2
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3. Produces new combination of alleles chromosomes and show ge-
4. Chromosomes separate at random netic variation. Explain how.
5. This produces varying combinations of genes (6)
6. Chromatids separated at meiosis II
14. 1. Refer to the specific individuals (using their num- Pedigree Questions Mark
ber) Scheme (3)
2. Explain what happened with the genes (passed
on recessive/dominant)
3. Describe the genotype of your examples and
mention their phenotype (homozygous/heterozy-
gous etc)
15. Group of organisms of the same species occupying Populations
a particular space at a particular time that can po-
tentially interbreed to produce fertile offspring.
16. The total number of genes of every individual in an Gene pool
interbreeding population.
17. How often an allele appears in a population. Allele frequency [defini-
tion][Equation] (2)
desired allele/total alleles = allele frequency (deci-
mal form)
18. No emigration or immigration Hardy-Weingberg Assump-
No mutations tions (4)
Mating is random
No natural selection
19. 1. Selection pressure exists in an environment Natural selection MS (7)
(name it)
2. Variation exists in stated phenotype of organ-
, AQA A-Level Biology Paper 2
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ism/ mutation occurs creating new alleles (name
the allele if applicable)
3. Some individuals have the selective advantage
(describe it)
4. Produces differential survival/ organisms with
successful alleles more likely to survive
5. Natural selection occurs via directional selection
6. Survivors breed and pass on alleles to offspring
7. Over time, there is a change in allele frequency
20. Favours the mean phenotype. (Normal distribution Stabilising selection
becomes narrower)
21. Favours one extreme end. (Normal distribution Directional Selection
translates that way)
22. Favours both extreme phenotypes. Mean is at dis- Disruptive Selection
advantage and dies. Can create two new species
23. 1. Natural disaster Genetic Drift: Bottleneck Effect
2. Few survive (4)
3. New population develops with different allele
4. Frequency to the original
24. Genetic drift that occurs after a small number of Founder effect
individuals colonize a new area. Allele frequency is
different to the original
25. 1. Populations geographically separated (forma- Allopatric speciation (4)
tion of a river) (Allopatric Speciation)
2. Separated populations now unable to repro-
duce
3. Different environments have different selective
, AQA A-Level Biology Paper 2
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pressures so each population will accumulate dif-
ferent beneficial mutations over time to help them
survive so change in allele frequency
4. Two populations become so genetically differ-
ent that they cannot reproduce to form fertile off-
spring, so are now classed as different species
26. Populations live in the same region but occupy dif- Reproductive isolation: Eco-
ferent habitats logical
27. Same area but are sexually mature at different Reproductive isolation: Sea-
times sonal
28. Different species ensure successful mating by spe- Reproductive Isolation: Behav-
cific courtship (bird dances). As this is genetic, mu- ioural
tation can change this
29. Plants exhibit pheromones to any mate with their Reproductive isolation: Incom-
own species patibility
30. Lack of fit between sexual organs in insects Reproductive Isolation: Incom-
patibility in Arthropods
31. 1. Occurs in the same habitat so sympatric specia- Lord Howe Island in the
tion Tasman Sea possesses two
2. Mutation causes different flowering times species of palm tree which
3. Seasonal Reproductive separation have arisen via sympatric spe-
4. No gene flow between the organisms so differ- ciation. The two species di-
ent alleles passed on. verged from each other after
5. Disruptive natural selection the island was formed 6.5 mil-
6. Eventually, different species cannot interbreed lion years ago. The flowering
to produce fertile offspring; times of the two species are
different.
Study online at https://quizlet.com/_cv2okl
1. Alleles that are neither dominant nor recessive to Codominant
one another, so both alleles are always expressed
in the phenotype.
2. The inheritance of a single gene Monohybrid inheritance
3. Physical, behavioural, biochemical expression of an Phenotype
organisms genotype
4. The type of genes an individual has Genotype
5. Alles that is always expressed in the phenotype Dominant
6. Only expressed in the phenotype when homozy- Recessive
gous
7. both alleles are the same Homozygous
8. Both alleles for a specific gene are different Heterozygous
9. Position of a gene on a chromosome Loci
10. A set of instructions for a specific polypeptide Gene
11. Different forms of a gene Allele
12. 1. Expected ratios are probability Suggest four reasons why ob-
2. Sexual reproduction is random due to random served ratios are not the same
fusion of gametes and random assortment homol- as expected ratios (4).
ogous chromosomes.
3. Small sample size
4. Linked genes
13. 1. Homologous chromosomes pair up Meiosis results in cells that
2. Crossing over / chiasmata form; have the haploid number of
, AQA A-Level Biology Paper 2
Study online at https://quizlet.com/_cv2okl
3. Produces new combination of alleles chromosomes and show ge-
4. Chromosomes separate at random netic variation. Explain how.
5. This produces varying combinations of genes (6)
6. Chromatids separated at meiosis II
14. 1. Refer to the specific individuals (using their num- Pedigree Questions Mark
ber) Scheme (3)
2. Explain what happened with the genes (passed
on recessive/dominant)
3. Describe the genotype of your examples and
mention their phenotype (homozygous/heterozy-
gous etc)
15. Group of organisms of the same species occupying Populations
a particular space at a particular time that can po-
tentially interbreed to produce fertile offspring.
16. The total number of genes of every individual in an Gene pool
interbreeding population.
17. How often an allele appears in a population. Allele frequency [defini-
tion][Equation] (2)
desired allele/total alleles = allele frequency (deci-
mal form)
18. No emigration or immigration Hardy-Weingberg Assump-
No mutations tions (4)
Mating is random
No natural selection
19. 1. Selection pressure exists in an environment Natural selection MS (7)
(name it)
2. Variation exists in stated phenotype of organ-
, AQA A-Level Biology Paper 2
Study online at https://quizlet.com/_cv2okl
ism/ mutation occurs creating new alleles (name
the allele if applicable)
3. Some individuals have the selective advantage
(describe it)
4. Produces differential survival/ organisms with
successful alleles more likely to survive
5. Natural selection occurs via directional selection
6. Survivors breed and pass on alleles to offspring
7. Over time, there is a change in allele frequency
20. Favours the mean phenotype. (Normal distribution Stabilising selection
becomes narrower)
21. Favours one extreme end. (Normal distribution Directional Selection
translates that way)
22. Favours both extreme phenotypes. Mean is at dis- Disruptive Selection
advantage and dies. Can create two new species
23. 1. Natural disaster Genetic Drift: Bottleneck Effect
2. Few survive (4)
3. New population develops with different allele
4. Frequency to the original
24. Genetic drift that occurs after a small number of Founder effect
individuals colonize a new area. Allele frequency is
different to the original
25. 1. Populations geographically separated (forma- Allopatric speciation (4)
tion of a river) (Allopatric Speciation)
2. Separated populations now unable to repro-
duce
3. Different environments have different selective
, AQA A-Level Biology Paper 2
Study online at https://quizlet.com/_cv2okl
pressures so each population will accumulate dif-
ferent beneficial mutations over time to help them
survive so change in allele frequency
4. Two populations become so genetically differ-
ent that they cannot reproduce to form fertile off-
spring, so are now classed as different species
26. Populations live in the same region but occupy dif- Reproductive isolation: Eco-
ferent habitats logical
27. Same area but are sexually mature at different Reproductive isolation: Sea-
times sonal
28. Different species ensure successful mating by spe- Reproductive Isolation: Behav-
cific courtship (bird dances). As this is genetic, mu- ioural
tation can change this
29. Plants exhibit pheromones to any mate with their Reproductive isolation: Incom-
own species patibility
30. Lack of fit between sexual organs in insects Reproductive Isolation: Incom-
patibility in Arthropods
31. 1. Occurs in the same habitat so sympatric specia- Lord Howe Island in the
tion Tasman Sea possesses two
2. Mutation causes different flowering times species of palm tree which
3. Seasonal Reproductive separation have arisen via sympatric spe-
4. No gene flow between the organisms so differ- ciation. The two species di-
ent alleles passed on. verged from each other after
5. Disruptive natural selection the island was formed 6.5 mil-
6. Eventually, different species cannot interbreed lion years ago. The flowering
to produce fertile offspring; times of the two species are
different.
