HB F-CHARLOTTE, AN A-GAMMA VARIANT WITH A THREONINE RESIDUE IN POSITION GAMMA-75 AND A GLYCINE RESIDUE IN POSITION GAMMA-136

Structural analyses of an abnormal gamma chain, present in a relative amount of approximately 10% in a cord blood sample of a Black newborn baby, identified two substitutions (gamma-75 Ile --> Thr and gamma-136 Ala --> Gly) in an apparent variant of the A-gamma chain. Gene mapping analysis of genomic DNA and hybridization with specific probes confirmed the presence of these two mutations and provided the evidence to indicate that the abnormal gamma chain was indeed a variant of A-gamma with the two listed mutations.