Different varieties of the same gene are called

In genetics, different varieties or alternative versions of the same gene are called alleles [1]. While a gene represents a specific genomic location or locus that determines a trait, alleles describe the specific variations that can exist at that location [2][3]. For instance, a gene for a trait like blood type may have multiple allelic forms such as A, B, and O. Every individual typically inherits two alleles for each gene—one from each parent [1]. If these two alleles are identical, the individual is homozygous; if they differ, the individual is heterozygous [1]. The term 'genotype' refers to the specific pair of alleles an individual possesses, whereas 'alleles' specifically denotes the different versions of the gene itself. Other options like isomers are chemical variants, and sib pairs refer to siblings in genetic studies.

Sources

1. [1] https://www.genome.gov/genetics-glossary/Allele
2. [2] https://www.ebi.ac.uk/training/online/courses/human-genetic-variation-introduction/what-is-genetic-variation/what-are-variants-alleles-and-haplotypes/
3. [3] https://pmc.ncbi.nlm.nih.gov/articles/PMC4450815/