1) Allele 2) Cistron 3) Factor 4) Gene 1) Allele 2) Gene 
See allele. 
• (n.) One of the pure unit characters commonly existing singly or in pairs in the germ cells of Mendelian hybrids, and exhibited in varying proportion among the organisms themselves. Allelomorphs which under certain circumstances are themselves compound are called hypallelomorphs. See Mendel`s law.
Synonym: allele. ... Origin: G. Allelon, reciprocally, + morphe, shape ... (05 Mar 2000) ... 
One of several alternative forms of a gene: commonly shortened to allele.
Al·le'lo·morph noun [ Greek ... of one another + Greek ... form.] (Biol.) One of the pure unit characters commonly existing singly or in pairs in the germ cells of Mendelian hybrids, and exhibited in varying proportion among the organisms themselves. Allelomorphs which under certain circumstances ...
Type: Term Pronunciation: ă-lē′lō-mōrf Synonyms: allele
allelomorph One of several alternative forms of the same gene, occupying the same relative positions in homologous chromosomes.