Question

3. In some varieties of sheep, the presence of horns is determined by an allele which behaves as dominant in males but recessive in females. If 96% of males are horned, what is the frequency of horned females? (6 marks)

Answer 1

The right answer to the frequency of female horned sheep is 32%.

Step-by-step explanation:

Let the allele responsible for horn in sheep generally be: x

and the complementary allele be: y

The production of these progeny is as a result of an underline-cross between their parents. Since the frequency of horned males is not 100%, it means that some males are hornless. This means that the parents of this filial generation are heterozygous: xy and xy, for both male and female parents.

When we use punnets square and cross these genotypes: it will lead to the following genotypic ratio: 1xx: 2xy: 1yy.

We were told that the allele only shows itself in the female when they are in duplicate only: xx (which is the meaning of recessive allele), but the male with xx and xy will be horned.

Since 96%, which is 3 out of 4 of the male progeny, are horned comprise of 1xx and 2xy only, Then only one out the three possibilities are expected to be horned if it's a female who is xx. Therefore, the frequency of female horned sheep will be 1/3 of 96, which will give us 32%.