A, B, D, R, T are genes located on 5 different chromosomes. In all cases, the capital letter allele is dominant to lower case allele (i.e. A is dominant to a). In the following cross: AaBbDdRrTt (1st parent) x AabbDdrrTT (2nd parent) What fraction of progeny will genotypically resemble the 2nd parent?

We can calculate the fraction of progeny that will resemble the second parent by drawing a square diagram for each of the given parent genes separately and then multiplying the required gene fractions together.

First Parent = AaBbDdRrTt

Second Parent = AabbDdrrTT

Parent Alleles A a

A AA Aa

a Aa aa

The progeny resembling the second parent genotype (Aa) = 2/4 = 1/2

Parent Alleles B b

b Bb bb

The progeny resembling the second parent genotype (bb) = 2/4 = 1/2

Parent Alleles D d

D DD Dd

d Dd dd

The progeny resembling the second parent genotype (Dd) = 2/4 = 1/2

Parent Alleles R r

r Rr rr

The progeny resembling the second parent genotype (rr) = 2/4 = 1/2

Parent Alleles T t

T TT Tt

The progeny resembling the second parent genotype (TT) = 2/4 = 1/2

Overall fraction of progeny that will genotypically resemble the second parent (AabbDdrrTT) = 1/2 x 1/2 x 1/2 x 1/2 x 1/2 = 1/32