In snail shells the direction of shell coiling is controlled by a maternal effec

Question

In snail shells the direction of shell coiling is controlled by a maternal effect gene. Two alleles, a dominant one, D, causes dextral (right handed) coiling, and a recessive one, d, causing sinistral (left hand) coiling.

Given three different female snails of genotypes DD, Dd, and dd, crossed with dd males.

What are the phenotypes of the offspring of each

DD females:

Dd females:

dd females:

What are the phenotypes of these females. Explain, based on the probable parental (both maternal and paternal for each female. (Hint: you may not be able to give definitive answers for each. If so explain why in terms of the possible parents.)

DD female:

Dd female:

dd female:

Explanation / Answer

Given three different female snails of genotypes DD, Dd, and dd, crossed with dd males.

1. Cross between DD femals and dd male will have the offspring with following genotypes:

Dd, Dd --------------> Right handed (dextral coiling) -----> 100%

2. Cross between Dd femals and dd male will have the offspring with following genotypes:

Dd, Dd --------------> Right handed (dextral coiling) -----> 50%, dd, dd --------> Left hand (Sinistral coiling).

3. Cross between dd femals and dd male will have the offspring with following genotypes:

dd, dd, dd, dd --------------> Left hand (Sinistral coiling).----> 100%

Phenotypes of the following genotypes are,

DD female: Right handed (dextral coiling)

Dd female: Right handed (dextral coiling)

dd female: Left hand (Sinistral coiling).

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