cis-trans test


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cis-trans test

 [sis trans]
a test in microbial genetics to determine whether two mutations that have the phenotypic effects, in a haploid cell or a cell with single phage infection, are located in the same gene or different genes; the test depends on the independent behavior of two alleles of a gene in a diploid cell or in a cell infected with two phages carrying different alleles.
Cis-trans click for a larger image
Fig. 104 Cis-trans test . The cis-trans test configurations. m1 and m2 are mutations. The two lines represent two homologous chromosomes.

cis-trans test

a genetic COMPLEMENTATION TEST to determine if two mutations have occurred within the same CISTRON or in adjacent cistrons. The test depends upon the two mutations being introduced into a cell at the same time. If they ‘complement’ each other by producing a WILD TYPE phenotype the mutations are in different cistrons (i.e. nonallelic). If a mutant phenotype is produced this shows the two mutations to be noncomplementary and therefore to be located in the same cistron (i.e. allelic). Two arrangements are possible in the cis-trans test (see Fig. 104 which can be carried out in a double HETEROZYGOTE individual (a HETEROKARYON in a haploid type). The more important is the transconfiguration, which is diagnostic, since two normal cistrons are present if the mutations are nonallelic (giving wild type) whereas the same cistron is mutant on both chromosomes if the mutations are allelic (giving a mutant phenotype).