[OLD] Populations - Inheritance: Exam Questions

Question 1

How many genetically different gametes can be produced by meiosis from a dell with the genotype Bb Cc Dd? Assume these genes are located on different pairs of homologous chromosomes. Show your working. (2)

Answer 1

2^3 = 8

Question 2

A breeder crossed a black male cat with a black female cat on a number of occasions. The female cat produced 8 black kittens and 4 white kittens.
Explain the evidence that the allele for white fur is recessive. (1)

Answer 2

1) Two black parents produced white kittens

2) Both black parents must be heterozygous

Question 3

A breeder crossed a black male cat with a black female cat on a number of occasions. The female cat produced 8 black kittens and 4 white kittens.
Predict the likely ratio of colours if kittens born to a cross between this black male and a white female. (1)

Answer 3

1: 1
black: white

Question 4

A chocolate female cat was crossed several times with a black female cat. They produced 11 black kittens, 2 chocolate kittens and 5 cinnamon kittens. The breeder had expected equal numbers of chocolate and cinnamon kittens. Explain why the actual numbers were different from those expected. (1)

Answer 4

1) Fertilisation is random

2) It’s a small sample

Question 5

The gene controlling coat colour in cats has three alleles. The allele B given black fur, the allele b gives chocolate fur, and the allele bi gives cinnamon fur.
Allele B is dominant to both allele b and bi.
Allele b is dominant to allele bi.
What phenotypes would cats have with the genotypes Bbi, bbi, Bb?

Answer 5

Bbi - black
bbi - chocolate
Bb - black

Question 6

The gene controlling coat colour in cats has three alleles. The allele B given black fur, the allele b gives chocolate fur, and the allele bi gives cinnamon fur.
Allele B is dominant to both allele b and bi.
Allele b is dominant to allele bi.
The breeder wanted to produce a population of cats that would all have chocolate fur. Is this possible? Explain your answer. (2)

Answer 6

1) Yes, by crossing two (bb) homozygous chocolate fur cats
2) But don’t know genotype of chocolate cat
3) Two chocolate cats could give cinnamon kittens

Question 7

Explain what is meant by a dominant allele. (1)

Answer 7

The alley expressed even when present with the recessive allele of the same gene

Question 8

In a species of snail, shell colour is controlled by a gene with three alleles. The shell may be brown, pink or yellow. The allele for brown, Cb, is dominant to the other two alleles. The allele for pink, Cp, is dominant to the allele doe yellow, Cy.
Give all the genotypes which would result in a brown-shelled snail. (1)

Answer 8

CbCb, CbCp, CbCy