At the selected site, each parent zygote had been assumed to have three possible states or gene pairs in probability 25-50-25.

The remaining 4586 gene pairs were missing in at least one genome.

The substitution rates for orthologous gene pairs were calculated using the same approach.

In this paper, we will focus on gene clusters of size two, that is, gene pairs.

Recessive traits require both genes in the gene pair to work together to control the trait.

Several gene pairs control the light versus dark hair color in a cumulative effect.

This ratio may differ, depending on the dominance conditions present in the original gene pairs.

Gene inter- action is the control of a trait by two or more gene pairs.

According to one theory, at least two gene pairs control human hair color.

"There are a lot of data not clearly explained by just two gene pairs," he said.