Chapter 3, Problem 25PDQ

When working out genetics problems in this and succeeding chapters, always assume that members of the P₁ generation are homozygous, unless the information or data you are given require you to do otherwise.

Two true-breeding pea plants are crossed. One parent is round, terminal, violet, constricted, while the other expresses the contrasting phenotypes of wrinkled, axial, white, full. The four pairs of contrasting traits are controlled by four genes, each located on a separate chromosome. In the F₁ generation, only round, axial, violet, and full are expressed. In the F₂ generation, all possible combinations of these traits are expressed in ratios consistent with Mendelian inheritance.

(a) What conclusion can you draw about the inheritance of these traits based on the F₁ results?

(b) Which phenotype appears most frequently in the F₂ results? Write a mathematical expression that predicts the frequency of occurrence of this phenotype.

(c) Which F₂ phenotype is expected to occur least frequently? Write a mathematical expression that predicts this frequency.

(d) How often is either P₁ phenotype likely to occur in the F₂ generation?

(e) If the F₁ plant is testcrossed, how many different phenotypes will be produced?