300 random blood samples collected from residents of Khartoum, Sudan, were analysed for 5 blood group systems, 4 serum proteins, 9 red cell enzymes, abnormal haemoglobins and beta-thalassaemia. The results suggest varying degrees of admixture of the local tribes by migration from the surrounding regions. Two samples showed a probable new variant of glucose 6-phosphate dehydrogenase (? GdB Khartoum) with normal red cell activity. In spite of the presence of a high degree of consanguinity in the population, there was no significant deviation from Hardy-Weinberg equilibrium in any of the polymorphic systems.

A total of 292 randomly selected subjects belonging to two indigenous Arab tribes (Harbi and Ghamid) and two immigrant tribes (Mograbi and Mowallad), residents in Western Saudi Arabia, have been tested for genetic variants of six blood groups, four serum proteins, and five red cell enzyme systems. The distribution of the polymorphic systems was different between indigenous and immigrant tribes, and the present Arab population shows a considerable degree of admixture from the surrounding countries, in particular Africa.

597 unrelated persons, comprising of 401 males and 196 females, were investigated for glucose-6-phosphate dehydrogenase (G6PD) and haemoglobin phenotypes by starch gel electrophoresis. The levels of G6PD activity were assayed in order to study the quantitative expression of G6PD phenotypes and the influence of haemoglobin phenotypes on such expression. There was no significant difference in the levels of G6PD activity in subjects with GdA or GdB. The mean levels of the enzyme activity were 165.5 ± 33.7 and 164.8 ± 33.8 1U/10¹² red cells in males and 159.3 ± 27.8 and 163.4 ± 33.5 IU/10¹² red cells in females, respectively. 14 subjects with Gd(+) ‘Khartoum’ had significantly (p < 0.001) higher level of enzyme activity with a mean above 200 IU/10¹² red cells. On the other hand, 20 subjects with GdB(int) (demonstrated by visual comparison of starch gel) showed significantly (p < 0.001) lower levels of enzyme activity (107.6 ± 23.5 IU/10¹² red cells). The heterozygotes GdAB also had slightly, but not significantly lower levels of enzyme activity than either GdA or GdB. The mean level of activity for GdAB was 140.1 ± 29.4 IU/10¹² red cells.

1,416 males and 564 female subjects from four Negroid and five Arab tribes and a group of mixed tribes of the Sudan were investigated for the phenotypic distribution of red cell glucose-6-phosphate dehydrogenase by starch gel electrophoresis. In general, the tribes of Negroid origin had higher frequency of Gd^A compared to the tribes of Arab ancestry. However, the Nilotes showed a lower frequency of Gd^A allele and the Mahass tribe claiming an Arab origin had a higher frequency of Gd^A. The immigrant groups from the neighbouring African countries also had a higher frequency of Gd^A. Gd^B (Khartoum) was present in low frequencies in both the Arab and Negroid tribes. A great deal of intratribal variation in the phenotypic distribution of G6PD was observed in the Nuba and Gáali tribes from different localities

A total of 1,112 randomly selected Saudi Arabs, of both sexes, living in Jeddah and the surrounding areas were screened for the phenotypic distribution of red cell glucose-6-phosphate dehydrogenase (G6PD) and 6-phosphogluconate dehydrogenase (6PGD). They were also investigated for haemoglobin and for thalassaemia. Phenotyping of the haemoglobins and the red cell enzymes was carried out by starch gel electrophoresis and the dye-decolouration screening test, while the investigation for thalassaemia was carried out by globin-chain biosynthesis, followed by column chromatography. The red cell Gd^– alleles were significantly associated with the sickle-cell gene in both the males (χ²₁: AS-28.80; SS-4.89) and females (χ²₁: AS-10.99; SS-13.16). A similar association was also observed between G6PD deficiency and thalassaemias in males (χ²₁: α-thalassaemia – 3.13; β-thalassaemia – 11.06) and females (χ²₁: α-thalassaemia – 6.63). However, no such association was detected between red cell 6PGD types and haemoglobin genes. The results suggest that the red cell G6PD deficiency, sickle-cell and thalassaemia genes might have evolved as a result of the same ecological factor, probably malaria.