ˈsiˌsträn noun
( -s )
Etymology: cis-tr ans + -on (II)
: a segment of DNA that is equivalent to a gene and that specifies a single functional unit (as a protein or enzyme) and within which two heterozygous and closely linked recessive mutations are expressed in the phenotype when on different homologous chromosomes but not when on the same chromosome
• cis·tron·ic siˈstränik adjective