What term describes one of a pair of genes that occupy the same location on homologous chromosomes?

The term that describes one of a pair of genes that occupy the same location on homologous chromosomes is "allele." Alleles are different forms of a gene that can exist at a specific locus on a chromosome. For example, if you consider the gene that determines flower color in plants, there may be an allele for red flowers and another allele for white flowers. These two alleles would be located at the same position on homologous chromosomes, influencing the trait that is expressed.

Haploid refers to a cell that contains one complete set of chromosomes, such as a sperm or egg cell, while diploid indicates a cell that has two complete sets of chromosomes, one from each parent. These terms relate to the number of chromosome sets in a cell rather than the concept of alleles at specific loci. Genus simply describes a category in biological classification and does not specifically pertain to genetic variations like alleles do. Thus, the most accurate term for a specific version of a gene located at the same position on homologous chromosomes is indeed allele.