Final answer:
The genes of a gene family consisting of two or more homologous genes are called paralogs. These are similar genes within an organism's genome that have arisen from gene duplication and may diverge to acquire new functions while retaining a similar sequence. They are distinct from orthologs, which are homologous genes in different species.
Step-by-step explanation:
The genes of a gene family that consist of two or more homologous genes are called paralogs. Paralogs arise due to gene duplication events within the same species, leading to a family of similar genes within a single organism's genome. These genes can then diverge and acquire new functions, although they retain a similar sequence due to their shared ancestry.
Human cells, for example, have 23 pairs of homologous chromosomes, with alleles that represent variations of genes. Alleles are different versions of genes that code for the same trait, and can be either identical (homozygous) or different (heterozygous) across the homologous chromosomes. The variation between alleles contributes to the diversity of traits seen within a species.
The term "homologs" refers to matched pairs of chromosomes that are similar but not identical, as they may contain different alleles. This term should not be confused with paralogs, which specifically refers to the homologous genes within a single genome, resulting from gene duplication. On the other hand, orthologs are homologous genes found in different species that evolved from a common ancestral gene, and they typically maintain the same function across the species.