Question

You are trying to breed and commercialize a new strain of the corn by combining several traits that your marketing team tells you consumers will like (Yellow kernels, Vitamin-rich, Protein-rich and Sweet). You know alleles of four genes as follows:

Yellow kernels, White kernels (“B gene”, allele dominance unknown)

Vitamin-rich, Vitamin-poor (“N gene”, allele dominance unknown)

Protein-rich, Protein-poor (“R gene” allele dominance unknown)

Sweet, Bland (“T gene”, allele dominance unknown)

You breed together a true-breeding Yellow kernel, vitamin-poor, protein-poor, sweet strain with a true-breeding white kernel, vitamin-rich, protein-rich, bland strain. The F1s all are Yellow kernels, vitamin-rich, protein-poor and bland. You self-cross the F1 lines to obtain F2 plants.

1. What fraction of the F2 generation will be Yellow kernels, vitamin-rich, protein-rich, sweet corn (show your work)?

2. Of the Yellow kernel, vitamin-rich, protein-rich, sweet corn individuals you identify within the F2 population, how many would you have to test to be 95% sure you have found at least one true breeding individual with those same characteristics (show your work)?

Answer 1

The yellow colour in corn kernels is formed in a layer of cells that are produced by the seed and thus contains genes from both the male and female parent. The white trait is recessive to yellow so a pollen grain carrying the yellow allele will produce a yellow seed in the ear made by a white mother plant.