Evolution of alpha and beta globin gene families by gene duplication
The globin gene loci
are part of a familty of duplicated and reduplicated genes. Myoglobin is
the main
oxygen-transporting molecule in muscle, and diverged from circulating
forms of the molecule in late deuterostome or early chordate history.
The alpha and beta families
diverged early in vertebrate history, at the time of the first fishes.
The alpha family comprises zeta ( 
), pseudo-zeta (
),
pseudo-alpha ( 
1),
and two alpha ( 2
, 1) loci. The beta family comprises epsilon (
),
two gamma (G
,
A),
pseudo-beta ( 
1),
delta ( 
), and beta (
)loci. In each family, the oldest globin locus is furthest 5' in the gene cluster: the predominant alpha and beta loci are furthest 3'
), pseudo-zeta (),
pseudo-alpha ( 1),
and two alpha ( 2
, 1) loci. The beta family comprises epsilon (
),
two gamma (G
,
A),
pseudo-beta ( 
1),
delta ( 
), and beta (
)loci. In each family, the oldest globin locus is furthest 5' in the gene cluster: the predominant alpha and beta loci are furthest 3'Figure & Text © 2006 by Steven M. Carr