allele By Ivan Suarez Robles 13 Nov, 2010 One of the different versions of a gene. All alleles for a particular gene code for the same trait, but they influence the trait in different ways. For example, different alleles for the hair color gene correspond to different hair colors.Related Articles: Glossary: dominanceHTT Promoter Mutation has a Bi-directional Effect on HD Age of OnsetIdentification of Genetic Modifiers that Alter Clinical Onset of Huntington’s DiseaseGlossary: markerHD in Japan