Table 2.
Types of Molecular Homology
| Homolog | Genes that are descended from a common ancestor (e.g., all globins) |
| Ortholog | Homologous genes that have diverged from each other after speciation events (e.g., human β- and chimp β-globin) |
| Paralog | Homologous genes that have diverged from each other after gene duplication events (e.g., β- and γ-globin) |
| Xenolog | Homologous genes that have diverged from each other after lateral gene transfer events (e.g., antibiotic resistance genes in bacteria) |
| Positional homology | Common ancestry of specific amino acid or nucleotide positions in different genes |
