Speciation in the Baboon and its Relation to “y-Chain Heterogeneity and to the Response to Induction of HbF by 5-Azacytidine

In the baboon (Papio species), the two nonallelic ‘y-genes produce “y-chains that differ at a minimum at residue 75. where isoleucine (“y-chain) or valine ( y) may be present. This situation obtains in baboons that are sometimes designated as Papio anubis, Papio hamadryas, and Papio papio. However, in Papio cynocephalus. although the “ychains are identical with those in the above mentioned types. the v chains have the substitutions ala -‘ gly at residue 9 and ala -‘ val at residue 23. The”y-chains of P. cynocephalus are called V yC to distinguish them from the v ,Achains of P. anubis. etc. A single cynocephalus animal has been found to have only normal 7-chains and LyC chains (that is, glycine in residue 9. valine in 23, and isoleucine in 75). When HbF is produced in response to stress with 5-azacytidine. P. anubis baboons respond with greater