What is "transheterozygote"

The term transheterozygote is used in modern genetics periodicals in two different ways. In the first, the transheterozygote has one mutant (-) and one wildtype allele (+) at each of two different genes (A-/A+ and B-/B+ where A and B are different genes). In the second, the transheterozygote carries two different mutated alleles of the same gene (A*/A', see example below). This second definition also applies to the term "heteroallelic combination".

Organisms with one mutant and one wildtype allele at one locus are called simply heterozygous, not transheterozygous.

Transheterozygotes are useful in the study of genetic interactions and complementation testing.