Chapter 21, Problem 4PDQ

A dark-red strain and a white strain of wheat are crossed and produce an intermediate, medium-redF_1. When the F₁ plants are interbred, an F₂ generation is produced in a ratio of 1 dark-red: 4 medium-dark-red: 6 medium-red: 4 light-red: 1 white. Further crosses reveal that the dark-red and white F₂ plants are true breeding.

(a) Based on the ratios in the F₂ population, how many genes are involved in the production of color?

(b) How many additive alleles are needed to produce each possible phenotype?

(c) Assign symbols to these alleles and list possible genotypes that give rise to the medium-red and light-red phenotypes.

(d) Predict the outcome of the F₁ and F₂ generations in a cross between a true-breeding medium-red plant and a white plant.