Probability

Abstract

Consider the process of sexual reproduction. Among the sperm of a male the cells differ in their genetic message, and the same is true for the reproductive cells in an ovary. As a consequence, the traits of descendants differ in many ways. As it depends on chance which of the reproductive cells combine to become a fertilized cell, the outcome cannot be predicted. Yet there is no chaos. If we count particular traits in a large number of descendants, we find some rules. For instance, we see that a trait known as “heterozygous” occurs in the descendants at a predictable ratio. The well-known rules by Mendel¹ can best be formulated by using probabihty theory.