Question

A geneticist is studying two traits in the fruit fly - eye color and wing shape. They perform a dihybrid cross. If the genes for these traits are not linked, what proportion of the F2 offspring will be expected to display the dominant phenotype for eye color and recessive phenotype for wing shape

Answer 1

Answer:

3/16

Explanation:

According to Mendel's law of independent assortment of genes, when a dihybrid cross involves two genes that assort independently and one of the parents is dominant for the two genes and the other is recessive, the phenotypic ratio of the offspring at F2 would be 9:3:3:1. The proportion of the offspring with the dominant parental traits would be 9/16, those with the recessive parental traits would be 1/16, while those with mixed traits would be 3/16 each.

Assuming the eye color is represented by E and the wing shape is represented by W. At F2

     EeWw    x    EeWw

E_W_ - 9/16 (dominant for both eye color and wing shape)

E_ww - 3/16 (dominant for eye color and recessive for wing shape)

eeW_ - 3/16 (recessive for eye color and dominant for wing shape)

eeww - 1/16 (recessive for both eye color and wing shape)

Hence, the proportion of the offspring with dominant phenotype for eye color and recessive phenotype for wing shape would be 3/16.