Allele and Cistron

Allele noun - (genetics) either of a pair (or series) of alternative forms of a gene that can occupy the same locus on a particular chromosome and that control the same character.

Cistron and allele are semantically related. In some cases you can use "Cistron" instead a noun "Allele".

Cistron noun - (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.

Allele and cistron are semantically related. Sometimes you can replace term "Allele" with "Cistron", this nouns are similar.