The V gamma chain of fetal hemoglobin of the orangutan

Previous studies suggested that orangutans have nonallelic structural genes for their gamma chains, because either a threonyl or an alanyl residue may occupy position 135. Further investigation has now detected that position 75 may have either an isoleucyl or a valyl residue. From available evidence, the isoleucyl and threonyl residues are in one chain an the valyl and alanyl in the other. Orangutans appear to be homozygous for the two types of nonallelic genes.