Debora M Primrose Solutions for Chapter: Genetics and Evolution, Exercise 4: Practice problems for Topic 10

The diagram shows a pair of homologous chromosomes during meiosis in a cell in the human testis. The positions of the alleles of some genes are indicated.

(a) (i) Draw the possible chromosomes that could be found in the gametes formed.

The diagram shows a pair of homologous chromosomes during meiosis in a cell in the human testis. The positions of the alleles of some genes are indicated.

(a) (ii) Identify in your diagrams in [i] which chromosomes are recombinant.

The diagram shows a pair of homologous chromosomes during meiosis in a cell in the human testis. The positions of the alleles of some genes are indicated.

(b) Explain the consequence of crossing over on variability.

Two genes determine the coat colour in mice. One gene controls whether the coat is coloured and the other controls the colour. The gene for coloured (C) is dominant over non-coloured or albino (c). Agouti (A) is for grey-coloured hair and is dominant over black (a). Albino mice (cc) do not have coat colour because these mice are unable to produce any colour.

a) Using a Punnet square, predict the possible genotypes for colour of coat of the offspring of a crossing of two agouti mice heterozygous for both genes.

Two genes determine the coat colour in mice. One gene controls whether the coat is coloured and the other controls the colour. The gene for coloured (C) is dominant over non-coloured or albino (c). Agouti (A) is for grey-coloured hair and is dominant over black (a). Albino mice (cc) do not have coat colour because these mice are unable to produce any colour.

(b) ldentify the possible phenotypes for the offspring in (a).

Starting from the concept of a gene pool, explain briefly how populations of early vertebrates could have evolved into different groups.