This idea is expressed by the classic slogan of Beadle: "one gene - one enzyme", or in the more sophisticated but cumbersome terminology of today: "one cistron - one polypeptide chain".    From Wordnik.com.  [Francis Crick - Nobel Lecture] Reference

They explicitely explain that streptomycin resistance is the result of the organisms singular rRNA cistron, which renders them with one reversible mutation from almost completely resistant/non-resistant.    From Wordnik.com.  [Browsing the Latest Issue of Scientific American] Reference

As I was grappling with some of the more technical passages that contained words like allele, nucleotide, cistron, and mitosis.    From Wordnik.com.  [The Full Feed from HuffingtonPost.com] Reference

~3-fold increase (p-value = 0.0031) in translation of the second cistron of the reporter compared to control experiments with β-galactosidase overexpression (.    From Wordnik.com.  [PLoS ONE Alerts: New Articles] Reference