Question

skin color in a fish is inherited by the pattern of incomplete dominance at a single color locus (one gene). fish homozygous for the 'blue allele' (cb) are dark blue. fish homozygous for the 'transparent allele' (ct) allele have clear or transparent skin. what is the ratio of phenotypes in the offspring of a heterozygous x heteroxygous (cbct x cbct) cross?

Answer 1

In a heterozygous cross of cbct x cbct fish demonstrating incomplete dominance, the expected phenotypic ratio would be 1 dark blue:2 light blue:1 transparent.

The question involves the concept of incomplete dominance in genetics, where the offspring's phenotype is a blend of the parents' phenotypes when heterozygous for a certain trait. In the provided fish example, when two heterozygous fish with genotype cbct (one blue allele and one transparent allele) are crossed, the expected phenotypic ratio of their offspring would mirror that of a Mendelian monohybrid cross with incomplete dominance.

Here's the breakdown for the cross cbct x cbct:

• cbcb (Homozygous blue): 1/4 of the offspring

• cbct (Heterozygous, hence a blend of blue and transparent, likely a lighter blue): 1/2 of the offspring

• ctct (Homozygous transparent): 1/4 of the offspring

Therefore, the expected phenotypic ratio would be 1 dark blue:2 light blue:1 transparent among the offspring.