Problem

Solutions For An Introduction to Genetic Analysis Chapter 4 Problem 22P

Step-by-Step Solution

Solution 1

A homozygous Drosophila with autosomal recessive alleles a, b, and c, is crossed with a male homozygous, for the corresponding wild-type alleles. The genes are linked in the same order.

The parental genotypes are: a b c/a b c x a⁺b⁺c⁺/a⁺b⁺c⁺

The F₁ heterozygous males are crossed with the heterozygous females. The F₁ genotype would be:

a ⁺ b ⁺ c ⁺ /a b c x a⁺b⁺c⁺/a b c

Step #2 of 6

The F₂ progeny obtained are:

a ⁺ b ⁺ c ⁺	1364
a b c	365
a b c⁺	87
a ⁺ b ⁺ c	84
a b⁺c⁺	47
a⁺ b c	44
a b⁺c	5
a ⁺ b c⁺	4

Step #3 of 6

Based on the phenotypes, the two genotypes of a⁺b⁺c⁺/a⁺ b⁺ c⁺ and a⁺b⁺c⁺/a b c cannot be distinguished. The frequency of a b c/a b c can be used to estimate the frequency of a⁺b⁺c⁺ gametes from the female.