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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 ''trans''heterozygous. Transheterozygotes are useful in the study of genetic interactions and complementation testing. ==Transheterozygous at two loci== A transheterozygote is a diploid organism that is heterozygous at two different loci (genes). Each of the two loci has one natural (or wild type) allele and one allele that differs from the natural allele because of a mutation. Such an organism can be created by crossing together two organisms that carry one mutation each, in two different genes, and selecting for the presence of both mutations simultaneously in an individual offspring. The offspring will have one mutant allele and one wildtype allele at each of the two genes being studied. Transheterozygotes are useful in the study of genetic interactions. An example from Drosophila research: the wing vein phenotype of a recessive mutation in the Epidermal growth factor receptor (Egfr), a gene required for communication between cells, can be dominantly enhanced by a recessive mutation in Notch, another cell-signalling gene. A transheterozygote between Egfr and Notch has the genotype ''Notch/+ ; Egfr/+'' (where ''Notch'' and ''Egfr'' represent mutant alleles, and + represents wildtype alleles). The dominant interaction between Egfr and Notch suggested that the Egfr and Notch signalling pathways act together within the cell to affect the pattern of veins in the fly's wings. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Transheterozygote」の詳細全文を読む スポンサード リンク
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