How did gene duplication produce different hemoglobin genes?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

A diagram showing the tentative evolutionary relationships among hominid species over the past four million years, with skull images and labeled species names connected by solid and dotted lines to indicate proposed evolutionary pathways. — phylogeny Tentative phylogenetic scheme for the evolution of the human lineage. Solid bars indicate the time ranges during which species are thought to have existed, based on fossil evidence. Dotted lines signify evolutionary relationships between hominin species that have been proposed on the basis of the fossil evidence.

The evolution of hemoglobin genes is a classic example of molecular phylogeny. These genes are homologous, meaning they originated from a single ancestral gene that underwent multiple rounds of gene duplication and subsequent divergence over time.1

Through these duplication events, the ancestral gene gave rise to two distinct families of polypeptides, now located on different chromosomes: one family on chromosome 11 (including the $ϵ$ , $γ$ , $β$ , and $δ$ chains) and another on chromosome 16 (including the $ζ$ and $α$ chains).1

Following duplication, these genes evolved to serve specialized physiological roles across different developmental stages, such as embryonic, fetal, and adult hemoglobin. The process also produced pseudogenes—sequences that share high similarity with functional genes but contain mutations, such as premature stop codons, that render them nonfunctional. This complex history is evidenced by the similarity in both the coding sequences and the noncoding regions separating them.1