FREQUENCIES OF PHENOTYPES, ALLELES AND GENOTYPES IN ABO AND Rh-D BLOOD GROUP SYSTEMS IN SELECTED ETHNIC GROUPS (AFAR AND TIGRAY) AMONG STUDENTS OF ABA’ALA SECONDARY SCHOOL, AFAR REGIONAL STAT

Frequencies of phenotypes, alleles and genotypes of ABO and Rh-D Blood Group systems are known to vary worldwide geographically, ethnically and from one population to another. Therefore, this study was aimed at assessing the frequencies of phenotype, allele and genotype in ABO and Rh-D Blood group system in selected ethnic groups (Afar and Tigray) amongs tudents of Aba’ala Secondary School, Zone Two, Afar Region, Ethiopia based on their purposively to participate in the study. A total of 500 students took part on a voluntary basis in the study, from each of whom ABO and Rh-D blood type was determined using agglutination reaction with antisera. Blood type frequencies were calculated as percentages and allele and genotype frequencies were estimated from the phenotype frequencies by assuming Hardy-Weinberg principle for each population and for the whole population. Allele and genotype frequencies were estimated from the observed phenotypic frequency for ABO and Rh-D blood group system. The overall ABO blood group phenotypic frequency distribution was A (0.33), B (0.19), AB (0.05) and O (0.43).The allelic frequency was IA (0.2199), IB (0.1285) and IO (0.6516) and the genotypic frequencies were I A I A (0.0483), I A I O (0.2865),I B I B (0.0166), I B I O (0.1674),I A I B (0 .0565) and I OI O (0.4276). Differences in allelic, phenotypic and genotypic frequencies of the ABO and Rh-D blood groups among the students of the two ethnic groups were tested by chi-square method. Blood type O was found at a highest frequency in each group. Blood type AB has the lowest phenotypic frequencies in both ethnic groups. The order of ABO blood group allele frequencies were IO > IA > IB in the overall samples and in each of the two ethnic groups. The allele frequencies of I O, I A , and I B in the total sample were f ound tobe, 0.6587, 0.2129, and 0.1284 respectively. With respect to Rhesus factor, Rh D positive was found as 95.19% and 94.74% for Afar and Tigray ethnic groups respectively. Finally, blood type O is the most readily available blood type in the study area