Biology 5090 · O Level · Inheritance

Inheritance — practice question

A is used for the dominant allele that lets a person detect the scent of a particular flower. The recessive allele, which prevents the flower scent from being smelt, is written as a.
(a(i))[1]

Using these letters, indicate the genotype of a woman who is not able to smell the flower.

(a(ii))[2]

Using these letters, indicate which alleles could be present in the gametes of a woman who is able to smell the flower.

(b)[2]

Fig. 4.1 displays some alleles on a section of the sex chromosomes of a woman and a man. In the space below, draw these alleles as they could be shown in a sperm cell carrying the Y chromosome.

(c)[2]

Fig. 4.2 illustrates how the alleles on one of the chromosomes could appear in a cell taken from another part of the man’s body. Allele B indicates a mutation. Suggest two possible causes of the mutation.

(d)[3]

Mutated alleles such as the one shown in Fig. 4.2 are usually recessive. Use your knowledge of genetics to explain why society discourages marriage between people who are closely related.

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