Wordnet 3.0
NOUN (1)
1. 
 (genetics) a segment of DNA that is involved in producing a polypeptide chain; 
 it can include regions preceding and following the coding DNA as well as introns between the exons; 
 it is considered a unit of heredity; 
- Example: "genes were formerly called factors"[syn: gene, cistron, factor]
WordNet (r) 3.0 (2006):
cistron
    n 1: (genetics) a segment of DNA that is involved in producing a
         polypeptide chain; it can include regions preceding and
         following the coding DNA as well as introns between the
         exons; it is considered a unit of heredity; "genes were
         formerly called factors" [syn: gene, cistron, factor]