Question

A maternal effect can cause the offspring phenotype ratio to depart from that of classic Mendelian inheritance. In a species of snail, the dominant allele N codes for right-handed shell coiling and recessive allele n codes for left-handed shell coiling. If an Nn female with right-handed shell coiling males with an Nn male, what is the shell coiling phenotypic ratio of their offspring?
a. 4 right-handed coil:0, left-handed coil
b. 3. Right-handed coil: 1.left-handed coil
c. 3.bidirectional coil: 1.left-handed coil
d. 0.right-handed coil: 4.left-handed coil

Answer 1

Answer:

A. 4 right handed coil:0, left- handed coil

Explanation:

According to MENDELION CROSS:

We will get  NN, Nn,Nn,nn

NN, Nn, Nn are the 3 right handed coiling and nn is left handed coiling.

But in case of shell coiling in snails, maternal inheritance is applied in which offspring is decided only by phenotype.

Maternal traits: Here,female parent has right handed shell coiling. so, all the offsprings will have the same.

Hence, the phenotypic ratio will be:

4 Right handed coil: 0 Left handed coil