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Genetics and evolution

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Question 11

In birds, sex is determined by the ZW ZW\,ZW chromosome system: males are homogametic (ZZZZZZ) and females are heterogametic (ZWZWZW). Feather patterning is controlled by a sex-linked gene on the Z Z\,Z chromosome, where the allele for barred feathers (ZBZ^BZB) is dominant over the allele for non-barred feathers (ZbZ^bZb). An autosomal gene controls comb shape, where the allele for rose comb (RRR) is dominant over the allele for single comb (rrr).

A geneticist crosses a barred female chicken with a rose comb (heterozygous for comb shape) and a non-barred male chicken with a single comb, as shown in the genetic diagram below:

Genetic Cross Diagram

Which of the following options correctly predicts the phenotypic ratio of the offspring from this cross?

All male offspring are barred and all female offspring are non-barred; within each sex, there is a 1:11:11:1 ratio of rose to single combs.

Both male and female offspring consist of barred and non-barred individuals in a 1:11:11:1 ratio; within each group, there is a 1:11:11:1 ratio of rose to single combs.

All male offspring are non-barred and all female offspring are barred; within each sex, there is a 1:11:11:1 ratio of rose to single combs.

There is a 1:1:1:11:1:1:11:1:1:1 ratio of barred rose, barred single, non-barred rose, and non-barred single individuals, with equal proportions of males and females in each class.

Genetics and evolution Questions

  1. A Level
  2. /Biology
  3. /Genetics and evolution