In legal terms, inheritance describes the wealth that parents leave, or pass on, to their children. In biology, the word refers to the genetic processes by which parents endow their children with specific traits, like height, hair color, eye color, and other characteristics. It is an everyday observation that children tend to resemble their parents in many ways, but it is equally obvious that the resemblance is not a simple one. Tall parents do not always produce tall children; children with blue eyes do not necessarily have parents with blue eyes.

Similarity and Difference

Yet, in humans and all other biological organisms, there are clear similarities between one generation and the next: Dogs always give birth to dogs; acorns always develop into oak trees; when a chicken's egg hatches, an infant chicken—not a duck or an eagle—emerges from the shell. In other words, each...