cis configuration /sis/ , 1. the presence of the dominant alleles of two or more pairs of genes on one chromosome and the recessive alleles on the homologous chromosome. 2. the presence of the mutant genes of a pair of pseudoalleles on one chromosome and the wild-type genes on the homologous chromosome. Compare coupling, trans configuration. 3. (in chemistry) a form of geometric or stereoisomerism in which two substituent groups are on the same side of a double bond or aliphatic ring. Also known as Z (zusammen) configuration. Also called cis arrangement, cis position.
