Chromosomes with one, two, three, and four fetal globin genes: molecular
and hematologic analysis
AV Hill, DK Bowden, DJ Weatherall and JB Clegg
Analysis of DNA from 852 Island Melanesians has revealed a high frequency
of single- and triple-gamma-globin genes in this population. Homozygotes
for triple- and single-gamma genes have normal hematologic findings, normal
hemoglobin F (HbF) levels, and when there is coexisting alpha thalassemia,
appropriate levels of Bart's Hb (gamma 4) at birth. In addition, we have
identified an individual with a quadruple-gamma gene chromosome who also
has a normal HbF level. All single-gamma genes were A gamma, all
triple-gamma genes G gamma G gamma A gamma, and the quadruple-gamma gene G
gamma G gamma G gamma A gamma. Analysis of G gamma:A gamma ratios in cord
bloods and HbF levels in adults showed that these additional gamma genes
are expressed and are down regulated appropriately by the fetal to adult Hb
switch. Analysis of the restriction enzyme haplotypes of these various
chromosomes indicates that intrachromosomal cross-overs are more likely to
have produced these variants than interchromosomal recombination events.
Volume 67,
Issue 6,
pp. 1611-1618,
06/01/1986
Copyright © 1986 by The American Society of Hematology