Globin
Gene Expression in Development
Developmental Expression of Globins - Multiple globin genes are expressed at different
times in human development (Figure 7.22).
In the early embryo, the hemoglobin genes expressed are those
for the embryonic chains, 
and 
. As the fetus develops, these chains are replaced
by 
and 
chains, and finally, at about the time
of birth, the chains are replaced by 
chains. In
addition, after birth a small amount of a 
chain is produced.
By age six months, the infant will have almost all 22 (adult) hemoglobin. These
developmental types of hemoglobin chain are slightly different,
and each is coded for by a separate gene in the human genome.
See also: Evolution
of Myoglobin/Hemoglobin Proteins
INTERNET
LINKS:
1. Human
Globin Genes
2. Globin
Gene Server