Some snail species' shells can have right-handed direction of shell coiling or left-handed direction of shell coiling. The direction of coiling depends on a protein deposited by the mother in the egg cytoplasm with DD and Dd mothers depositing a protein that directs right-handed direction of coiling in shells. If Dd egg-producing snail and a dd sperm-producing snail mate what genotype(s) and phenotype(s) of offspring will result?
A) 1/2 Dd:1/2 dd; all right-coiling
B) all Dd; all right-coiling
C) 1/2 Dd: 1/2 dd; half right-coiling and half left-coiling
D) all Dd; half right-coiling and half left-coiling

Question

Quizplus · Accepted Answer

The Dd egg-producing snail will produce 1/2 D eggs and 1/2 d eggs. The dd sperm-producing snail will produce only d sperm. Therefore, the possible genotypes of the offspring are 1/2 Dd and 1/2 dd. Since D is dominant, all offspring will have right-coiling shells.

Some Snail Species' Shells Can Have Right-Handed Direction of Shell