What do we call the different forms of a gene found at the same locus on homologous chromosomes?

The term for different forms of a gene located at the same position (locus) on homologous chromosomes is "alleles." Alleles are variations of a gene that can result in different traits being expressed. For example, a gene that determines flower color in a plant may have a red allele and a white allele, leading to phenotypic variations in the color of the flowers depending on which alleles are present.

In the context of genetic inheritance, organisms typically receive two alleles for each gene, one from each parent. The combination of these alleles contributes to an individual's genotype and can influence their phenotype, which refers to the observable characteristics resulting from the interaction of the genotype with the environment. The other terms listed do not accurately describe this genetic phenomenon: genotypes refer to the specific allelic combinations in an individual, phenotypes describe the physical expression of traits, and homologs refer to the paired chromosomes themselves, not the variations of the genes they carry.