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JG Gilman and TH Huisman
The gamma-chains of fetal hemoglobin (HbF) of newborn babies are composed
of about 70% G gamma and 30% A gamma. In most babies, the G gamma value
declines postnatally to 40%, but in about 20% of black SS patients from
Georgia, 5 years and older, the G gamma level remains high at 60%.
Moreover, some 3% to 4% of black newborns have high G gamma values of 85%.
PstI digestion of DNA of one such high G gamma baby and of one normal
newborn showed the former to be heterozygous for the -G gamma-G gamma- and
-G gamma-A gamma-chromosomes. Only about one fourth of high G gamma SS
patients were such heterozygotes, while three fourths were -G gamma-A
gamma-/-G gamma-A gamma-homozygotes. Analysis of DNA of 38 SS patients
without the -G gamma-G gamma-chromosome showed a correlation of G gamma
values with genotype at one polymorphic restriction site: at the HincII
site in the psi beta gene, all -G gamma- A gamma-/-G gamma-A
gamma-homozygotes with high G gamma were +/- or +/+, while low G gamma
individuals were all -/-. Family studies, involving analyses at four
polymorphic sites (HindIII sites in the G gamma and A gamma genes and
HincII sites in the psi beta gene and 3' to it), suggested the association
of an unidentified high G gamma genetic determinant with haplotype + - + +.
This indicates that a genetic factor causing high G gamma levels in SS
patients is closely linked to the -G gamma-A gamma-psi beta region of the
beta-globin gene cluster.
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| Copyright © 1984 by American Society of Hematology Online ISSN: 1528-0020 | |||||||||