Hardy-Weinberg ratio
The ratio of genotype frequencies that evolve when mating is random and neither selection nor drift are operating. For two alleles (A and a) with frequencies p and q, there are three genotypes: AA, Aa, and aa. The Hardy-Weinberg ratio for the three is: p2AA : 2pqAa : q2aa. It is the starting point for much of the theory of population genetics.

Harvey, Ralph
A geologist whose work includes the study of geological processes at a range of scales, from the smallest nanometer to broader-scale interpretations of the history experienced by geological materials

Hemoglobin
A protein that carries oxygen from the lungs throughout the body.

Helix-turn-helix motif
The structure of the DNA-binding region of one family of DNA binding protein.

Helicase
An enzyme that unwinds a DNA double of DNA polymerase III.

Heritable
Partly or wholly determined by genes; capable of being passed from an individual to its offspring.

Heritability
Broadly, the proportion of variation (more strictly, variance) in a phenotypic character in a population that is due to individual differences in genotypes. Narrowly, it is defined as the proportion of variation (more strictly, variance) in a phenotypic character in a population that is due to individual genetic differences that will be inherited in the offspring.
2. An attribute of a quantitative trait in a population that expresses how much of the total phenotypic variation is due to genetic variation.

Herrnstein, Richard J.
A professor of psychology and an author f n table books on intelligence and crime. He has primarily done research on human and animal motivational and learning processes. His books include Psychology and I. Q. in the Meritocracy, and he coauthored (with Charles Murray) The Bell curve: Intelligence and Class Structure in American Life (1994).