Question

In the endangered African watchamakallit, the offspring of a true-breeding black parent and a true-breeding white parent are all gray. When the gray offspring are crossed among themselves, their offspring occur in a ratio of 1 black :2 gray:1 white. Upon close examination of the coats, each hair of a gray animal is gray. What is the mode of inheritance?

1) one gene pair with black dominant to white
2) one gene pair with codominance
3) one gene pair with incomplete dominance
4) two gene pairs with recessive epistasis

Answer 1

The inheritance pattern exhibited by the African watchamakallit, given the 1 black : 2 gray : 1 white ratio in offspring, is incomplete dominance, where the heterozygous gray offspring show a blend of the black and white phenotypes.

Step-by-step explanation:

The mode of inheritance for the African watchamakallit, based on the 1 black : 2 gray : 1 white phenotypic ratio among the offspring, indicates incomplete dominance. In this case, neither the black nor the white color is completely dominant. Instead, the heterozygous offspring (gray) exhibit a blend of the parents' phenotypes. This scenario mirrors human hair texture inheritance, where a child inherits one allele for curly hair and one for straight hair, resulting in wavy hair - an intermediate phenotype.

Following a cross of true-breeding black (homozygous dominant) and true-breeding white (homozygous recessive) parents, the F1 generation all display the intermediate gray phenotype. When two gray F1 individuals are mated (heterozygous), the distribution of the coat color of the offspring—1 black : 2 gray : 1 white—further supports the pattern of incomplete dominance, rather than codominance or epistasis, as seen with other genetic traits in mice.