Medical Definition of cis
1: characterized by having certain atoms or groups of atoms on the same side of the longitudinal axis of a double bond or of the plane of a ring in a molecule
2: relating to or being an arrangement of two very closely linked genes in the heterozygous condition in which both mutant alleles are on one chromosome and both wild-type alleles are on the homologous chromosome—compare trans 2
Medical Definition of CIS
carcinoma in situ
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Dictionary: Definition of "cis"
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