Chapter 3, Problem 1PDQ

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.

HOW DO WE KNOW?

In this chapter, we focused on the Mendelian postulates, probability, and pedigree analysis. We also considered some of the methods and reasoning by which these ideas, concepts, and techniques were developed. On the basis of these discussions, what answers would you propose to the following questions:

(a) How was Mendel able to derive postulates concerning the behavior of “unit factors" during gamete formation, when he could not directly observe them?

(b) How do we know whether an organism expressing a dominant trait is homozygous or heterozygous?

(c) In analyzing genetic data, how do we know whether deviation from the expected ratio is due to chance rather than to another, independent factor?

(d) Since experimental crosses are not performed in humans, how do we know how traits are inherited?