3. Corn snakes show variety in their skin color pattern. While the complete genetics of corn snake color are complex, the most common colors on normal corn snakes – red and black – are each coded by one gene. For the red gene, the allele for the presence of red pigment (R) is dominant and the allele for the absence of red pigment (r) is recessive. Likewise, for the black gene, the allele for the presence of black pigment (B) is dominant and the allele for the absence of black pigment (b) is recessive.
a. Draw the Punnett Square for the cross of a snake that is homozygous dominant for the red color with a snake that is heterozygous for the red color. What percentage of the offspring is expected to have red pigment in their skin?
b. Draw the Punnett Square for the cross of two snakes that are heterozygous for the black color. What percentage of the offspring are expected to have black pigment in their skin?
c. The parent snakes in part (b) that are heterozygous for black color are both homozygous recessive for the red gene. Each parent has genotype rr for the red gene. Based on this information, what percentage of their offspring are expected to lack both the red and black pigments in their skin? Explain your reasoning.