Abstract
The frequency of RhD and Rhd alleles of Rh blood group gene was estimated in 44 human populations distributed all over the world from the RhD phenotypic data. The average frequency of RhD and Rhd allele over these populations was 0.70 and 0.30, respectively. Higher frequency of RhD allele than the expected estimate (0.50) in all the populations, under Hardy-Weinberg equilibrium condition assuming equal frequency of both alleles in the initial population, indicated inbreeding at RhD/d locus as well as natural selection for RhD allele. Very high heritability estimate (84.04%) of Rh allele frequency revealed that this trait was under weak selection pressure and resulted in greater genetic variation in existing populations. It is consistent with Fisher’s fundamental theorem of natural selection. The results from the present study suggest that inbreeding at RhD/d locus and some other factors (possibly mutation, migration and genetic drift) other than natural selection alone played major roles in changing the Rh allele frequency in these populations.
Highlights
Rh system is one of the most complex human blood group systems and it is genetically controlled
In the existing populations the RhD allele on an average occurred 2.33 fold more than Rhd allele indicating that inbreeding might have occurred in RhD/d locus, thereby increasing the frequency of RhD allele
This increase could result from the natural selection for RhD allele in these populations
Summary
Rh system is one of the most complex human blood group systems and it is genetically controlled. In identification and transfusion practices, Rh blood group typing in man is routinely done. Human beings are broadly categorized as Rh +ve and Rh –ve following blood tests depending on the presence or absence of Rh-antigen or Dantigen. An Rh +ve individual produces D-antigen whereas the Rh –ve individual fails to produce D-antigen on RBC. D-antigen (Rho) is clinically the most important in the Rh system because it is highly antigenic. Other common Rh antigens are C, c, E and e. These are less immunogenic than the Dantigen. D is considered to be the most potent immunogen followed by c and E.
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