Question

In guinea pigs, dark hair (D) is dominant over light hair (d) and curly hair (C) is dominant over smooth hair (c). Complete a dihybrid cross for parents with the genotypes: DdCc × DdCc and answer the following in complete sentences.

1. Describe how you would set up a Punnett square for this cross.
2. List the likelihood of each possible offspring genotype.
3. List the likelihood of each possible offspring phenotype.

Answer 1

First you need to see how the alleles can exist on their own. So FOR DdCc you can get:
DC
Dc
dC
dc
the above alleles is what you do the cross with. In my diagram I will replace small c with u so that it doesn't get confusing, so you are crossing:
DC
Du
dC
du

DDCC 1 = 6.25% Dark curly hair
DDCu 2 = 12.5% Dark curly hair
DdCC 2 = 12.5% Dark curly hair
DdCu 4 = 25% Dark curly hair
DDCu 1 = 6.25% Dark curly hair

DDuu 2 = 12.5% Dark smooth hair

ddCC 1 = 6.25% light curly hair
ddCu 2 = 12.5% light curly hair

dduu 1 = 6.25% light smooth hair

The likelihood/probability of dark curly hair is 62.5%
The probability of dark smooth hair is 12.5%
The probability of light curly hair is 18.75%
The probability of light smooth hair is 6.25