gene family A group of similar or identical genes, usually along the same chromosome, that originate by gene duplication of a single original gene. Some members of the family may work in concert, others may be silenced and become pseudogenes. For example, each of the α- and β-haemoglobin families of humans includes members that duplicate each other's functions, act at different stages of the life cycle, or may have lost their function altogether.

gene family (multigene family) A group of genes that have arisen by duplication of an ancestral gene. Such genes show similarities of nucleotide sequence that betray their common origin, and if they have evolved relatively recently they occur close together on the same chromosome. However, more distantly related members of a gene family may be found scattered widely on different chromosomes, reflecting chromosomal rearrangements during the evolution of the genome. Members of a gene family may be functionally very similar or differ widely. For example, members of the histone gene family all produce very similar proteins, whereas the serine protease family contains both trypsin, the proteolytic digestive enzyme, and haptoglobin, a protein that binds globin but has no proteolytic activity.

gene family A group of similar or identical genes, usually along the same chromosome, that originate by gene duplication of a single original gene. Some members of the family may work in concert, others may be silenced and become pseudogenes.