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

B. 3. Right-handed coil: 1.left-handed coil

Explanation:

Phenotype is what you see - the visible or observable expression of the results of genes, combined with the environmental influence on an organism's appearance or behavior.

When Nn is crossed with Nn, they will produce offspring with NN, Nn, Nn and nn genotype.

N - Dominant allele

n - recessive allele

The phenotypic ratio of this offspring is 3 right-handed coil and 1 left-handed coil.

B. 3 right-handed coil: 1 left-handed coil

Explanation:

Female genotype : Nn

Male genotype: Nn

N: dominant allele (right handed coil)

n: recessive allele (left handed coil)

When we cross the Male (Nn) x Female (Nn) the phenotypic ratio will be right handed coil 3 : left handed coil 1.

  Solution:

                               Nn     x       Nn

Four possible genotypes = NN, Nn, Nn, and nn

So, NN = right handed coil

Nn (2) = right handed coil

nn= left handed coil

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