Hets

In genetics, a het (plural hets) refers to a heterozygous genotype at a particular genetic locus, meaning the two alleles carried by an individual are different (for example Aa or Bb). Het status is a locus-specific designation; an organism can be heterozygous at some loci while homozygous at others.

Het is typically determined through genetic testing or sequencing. In reporting, a person or organism is described as heterozygous for a marker when they possess one copy of each allele. In diploid organisms, each individual inherits one allele from each parent, and het status arises when the inherited alleles are not identical. Notation often marks the heterozygous state as het for a given locus, alongside explicit allele pairs (e.g., Aa).

Phenotypic effects in heterozygotes depend on the relationship between the alleles. In many cases, a heterozygote displays the dominant phenotype associated with one allele, as in complete dominance. In other cases, dominance is incomplete, producing an intermediate phenotype (for example, pink flowers in Aa plants). In still other situations, both alleles are expressed (codominance). Heterozygotes can also have fitness advantages in certain environments, a phenomenon known as heterozygote advantage or overdominance.

In population genetics, hets contribute to genetic diversity and are described by Hardy-Weinberg expectations under conditions of random mating and no selection. For a biallelic locus with allele frequencies p and q, the expected heterozygote frequency is 2pq. Identifying hets is important in breeding, disease association studies, and evolutionary analyses, as they influence inheritance patterns and genetic variation within populations.

Note: in genetics, hets refers specifically to heterozygous genotypes; the term is unrelated to other uses of “het” in different contexts.