Anomaly in the γ chain heterogeneity of the newborn

Abstract

The two types of γ chain in human foetal haemoglobin (HbF) are the products of nonallelic structural genes and have either glycine (Gγ type) or alanine (Aγ type) in position 136 (ref. 1). Although the examination of 108 cord blood samples from worldwide sources showed 102 to have a Gγ : Aγ ratio within a relatively narrow range, one had a low ratio and five a high ratio2. It seemed possible that analytical error was responsible for these extreme values. But as we studied cord blood from normal black babies of residents from Burke County, Georgia, where an abnormal HbF (designated FX (ref. 3)) has been detected repeatedly, we observed high ratios in further samples. The present study of almost 700 cord bloods has detected the high Gγ : Aγ ratio in about 7.5% of samples from black newborns as compared with perhaps 0.5% from Caucasian infants.