1 markWhat is the definition of codominance in genetics?
Where a heterozygous individual expresses two different alleles at the same time
Where a homozygous individual expresses two different alleles at the same time
Where one allele is dominant to another allele
Where an individual inherits two different alleles of the same gene
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1 markHow does meiosis introduce genetic variation between gametes?
| 1 | Replication of the Chromosomes |
| 2 | Crossing-over of non-sister chromatids |
| 3 | Independent assortment of homologous chromosomes |
1, 2 and 3
Only 1 and 2
Only 2 and 3
Only 1
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1 markDomestic cats inherit sex-linked genes for some fur colours. For example, the gene for orange fur is XB, and is dominant to the gene for black fur, Xb. A female cat with the genotype XBXb has patches of orange and black fur, known as tortoiseshell.
The below table shows a Punnett square of the inheritance of fur colour when a tortoiseshell female and an orange male are crossed.
| Mother: XBXb | |||
| Gametes | XB | Xb | |
| Father: XBY | XB | XBXB | XBXb |
| Y | XBY | XbY | |
What is the phenotype of the kitten indicated in the highlighted cell?
Orange female
Tortoishell male
Orange male
Black male
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1 markWhat is/are the function(s) of the Hardy-Weinberg equation?
| 1 | It can be used to calculate the frequency of alleles in a population |
| 2 | It can predict how allele frequency might change over time |
| 3 | It states that the frequency of alleles in a population will not change over time |
1, 2 and 3
Only 1 and 2
Only 2 and 3
Only 1
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1 markWhat is the definition of allopatric speciation?
Speciation which results from a change in behaviour in a population
Speciation which results from a non-physical barrier, which prevents members of the same species from producing fertile offspring
Where there is a change in allele frequencies in a population due to random chance
Speciation which results from a physical barrier, which prevents members of the same species from producing fertile offspring
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1 markA species of butterfly has one gene W, controlling wing spot colour and another E, controlling eye colour.
The dominant allele, W, produces black spots while the recessive allele, w, produces grey spots.
The dominant allele, E, produces black eyes while the recessive allele, e, produces brown eyes.
A black-spotted, brown-eyed butterfly is crossed with a grey-spotted, black-eyed butterfly. The offspring are all black-spotted and black-eyed.
What could potentially explain the cause of the offspring phenotype?
A heterozygous dihybrid cross
Autosomal linkage
Dominant epistasis
Sex linkage of both genes
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1 markA species of tropical bird has two genes involved in plumage colour, R and D.
The dominant allele R codes for red pigment in wing feathers, while the recessive allele, r codes for yellow pigment in the wing feathers.
The dominant allele D codes for an enzyme involved in pigment deposition, while the recessive allele d does not produce the enzyme involved in pigment deposition, resulting in white feathers.
If two double heterozygous red-winged birds breed, what will be the likely phenotypic ratio of the offspring?
9:3:3:1
9:3:4
1:1
3:1
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1 markIn birds, females have ZW sex chromosomes and males have ZZ sex chromosomes. A gene present on the Z chromosome, G, affects the speed of feather growth in young chickens. The dominant allele, G causes fast growth while the recessive allele, g causes slow growth.
If a male chicken with genotype ZG Zg breeds with a female with the genotype Zg W, what will be the phenotypes of the offspring that they produce?
Slow-feathering males and fast-feathering females
Fast-feathering males and slow-feathering females
Fast-feathering males, fast-feathering females and slow-feathering females
Slow-feathering males, fast feathering males, fast-feathering females and slow feathering females
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1 markWhich of the following statements accurately differentiate the nature of discontinuous variation from the nature of continuous variation?
| 1 | It is highly heritable, with no direct environmental influence |
| 2 | A very small number of gene loci are involved |
| 3 | It involves quantitative differences in characteristics |
| 4 | Different genes involved have an additive effect on the phenotype |
1 and 4 only
1 and 2 only
1, 2 and 3 only
3 and 4 only
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1 markA population of newts is divided into two separate populations over time by the formation of a large mountain range which the newts cannot cross. On one side of the mountain range, the temperature is cold and most of the newt’s available food is large terrestrial arthropods. On the other side of the mountain range, the temperature is warmer and the newt’s available food is largely small aquatic arthropods.
At what point would speciation occur?
When the two populations can no longer interbreed were they to come into contact
When gene flow is no longer possible as a result of geographical isolation
When each population is exposed to different selective pressures on each side of the mountain range.
When allele frequencies change in each population as they adapt to the different conditions on each side of the mountain range.
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1 markScientists self-pollinated some pea plants that were heterozygous for the gene controlling height.
They expected a 3:1 ratio of tall plants to short plants in the offspring.
1046 plants grew in the next generation. 798 were tall and 248 were short.
Which of the following, A to D, is a statistical test that could be used to determine if these numbers are significantly different from a 3:1 ratio?
chi-squared
Spearman’s rank
standard deviation
Student’s t-test
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1 markWhich of the following is not associated with the use of artificial selection in farm animals?
health problems in more productive breeds
inbreeding
increased frequency of mutations
reduced gene pool
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1 markThe ability to roll one’s tongue is under the control of a single gene. The gene has two alleles R and r.
People who can roll their tongues can have the genotypes RR or Rr. People who cannot roll their tongues have the genotype rr.
A survey by a student showed that 12% of the population in a single school cannot roll their tongues.
The student then used the Hardy-Weinberg principle to calculate the number of heterozygous individuals in the school.
Which of the following represents the percentage of heterozygous individuals at the student’s school?
Use the equations: p + q = 1 and p2 +2pq + q2 = 1
21.1%
22.7%
42.8%
45.3%
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1 markSelection pressure can affect homozygous individuals. The effect can be investigated using a model gene pool.
A large gene pool is necessary to ensure that
genetic drift can occur if frequency is higher.
homozygous individuals are present in high frequency.
the effect of chance variations in gene frequencies are minimised.
Hardy–Weinberg equilibrium is achieved.
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1 markIn a breeding experiment, a tall, round seeded (homozygous dominant) pea plant was crossed with a short, wrinkled seeded (homozygous recessive) pea plant. The F1 dihybrid plants were then used in a test cross.
If the genes are always linked and no crossing over occurs, what would be the predicted ratio in the F2 generation?
9 : 3 : 3 : 1
1 : 1 : 1 : 1
3 : 1
1 : 1
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1 markIn a variety of roses, P is the allele for pink petal colour and D is the allele for double flower. The genes are not linked.
Which cross will give a 1:1:1:1 ratio of phenotypes in the offspring?
PpDd x ppDd
PpDd x PpDd
PPdd x ppDD
Ppdd x ppDd
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1 markLong hair in a species of rabbit is caused by the presence of the allele HL. These rabbits have either very long hair or moderately long hair. The 'wild-type' short-haired rabbit possesses the allele HS.
The diagram below shows the results of two crosses involving one female and two male rabbits. 
Use the pedigree diagram to identify which row of the table below shows the correct phenotypes for the rabbits with genotypes HLHL and HLHS
|
HLHL |
HLHS |
|
| A |
Long hair |
Moderately long hair |
| B |
Moderately long hair |
Short hair |
| C |
Moderately long hair |
Long hair |
| D |
Long hair |
Short hair |
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1 markAubergine (Solanum melongena L.) belongs to the same family as potatoes and tomatoes.
Scientists were studying two inherited traits of the aubergine plants,
A pure-breeding non-prickly stemmed round fruit aubergine and a pure-breeding prickly stemmed linear fruit aubergine were crossed. All the F1 offspring were non-prickly stemmed with round fruit.
When members of the F1 generation were crossed, the F2 generation included 27 aubergine with non-prickly stems and linear fruit.
Which of the options, A to D, shows the observed results that most closely match the expected results for the number of non-prickly stemmed round fruit aubergines and prickly stemmed round fruit aubergines?
92 non-prickly stemmed round fruit aubergine and 31 prickly stemmed round fruit aubergines
27 non-prickly stemmed round fruit aubergines and 29 prickly stemmed round fruit aubergines
86 non-prickly stemmed round fruit aubergines and 11 prickly stemmed round fruit aubergines
27 non-prickly stemmed round fruit aubergines and 88 prickly stemmed round fruit aubergines
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1 markWhich of the following events takes place during prophase 1 of meiosis and contributes to an increase in genetic variation?
Crossing over of sister chromatids
Independent assortment of homologous chromosomes
Crossing over of non-sister chromatids
Independent assortment of chromatids
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1 markA number of events occur for a new species to emerge in a population.
Which of the following statements correspond to events that are involved in the formation of a new species?
Statement 1: Gene mutation
Statement 2: Selection pressure
Statement 3: A change in the environment
Statement 4: A large population size
1, 2, 3 and 4
Only 1 and 2
Only 1, 2 and 3
Only 1
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