A length of DNA that contains the information for coding a specific polypeptide chain or a functional RNA molecule (i.e. transfer RNA or ribosomal RNA). In the case of a protein, a cistron codes for a messenger RNA (mRNA) molecule. It is equivalent to the coding region(s) of a gene. The cistron as a unit of function was defined by the cis-trans test: mutations occurring within a cistron affect the same function.
Subjects: Biological Sciences.