Imagine that beak color in a finch species is controlled by a single gene. You mate a finch homozygous for orange (pigmented) beak with a finch homozygous for ivory (unpigmented) beak and get numerous offspring, all of which have a pale, ivory-orange beak. This pattern of color expression is most likely to be an example of
A) incomplete dominance.
B) codominance.
C) pleiotropy.
D) polygenic inheritance.

Question

Quizplus · Accepted Answer

Incomplete dominance is when the heterozygous phenotype is a blend of the two homozygous phenotypes. In this case, the offspring have a pale, ivory-orange beak, which is intermediate between the orange and ivory beak colors of the parents. Codominance is when both alleles are expressed equally in the heterozygous phenotype, which is not the case here. Pleiotropy refers to a single gene affecting multiple phenotypic traits, which is not relevant to the given scenario. Polygenic inheritance involves the contribution of multiple genes to a single trait, which is also not relevant in this case as only one gene is controlling beak color.

Imagine That Beak Color in a Finch Species Is Controlled