1. The smallest functional unit of heritability; a length of chromosomal DNA associated with a single biochemical function. Under classical concepts, a gene might consist of more than one c.; in modern molecular biology, the c. is essentially equivalent to the structural gene. 2. The genetic unit defined by the cis/trans test. [cis tr-ans + -on]
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cis·tron 'sis-.trän n a segment of DNA that is equivalent to a gene and that specifies a single functional unit (as a protein or enzyme)
cis·tron·ic sis-'trän-ik adj
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n.
the section of a DNA or RNA chain that controls the amino-acid sequence of a single polypeptide chain in protein synthesis. A cistron can be regarded as the functional equivalent of a gene.
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cis·tron (sisґtron) [L. cis on this side + trans on the other side + Gr. on neuter ending] originally, a unit of genetic material determined by a cis-trans test; it has been shown to be essentially equivalent to a gene (q.v.).Medical dictionary. 2011.