We present here a new interesting feature of the human tumor suppressor gene p53: a very pronounced ethnic and clinal variation of polymorphic codon 72 alleles. The frequency of the A1 (Pro) allele showed a north-south cline from 17% in Swedish Saamis to 63% in African Blacks (Nigerians), and there was a significant (p < 0.001) correlation (r = 0.95) between the A2 frequency and latitude. In the Finnish and Swedish populations no significant differences were found with respect to the genotype and allele distributions in spontaneously aborted fetuses and liveborn children, which makes differential intrauterine selection unlikely. However, the ethnic and clinal variations suggest that the codon 72 polymorphism is balanced and maintained by natural selection.
A total of 213 Kadar from a number of villages in the Anamalai Hills, South India have been tested for 4 blood group, 5 serum protein and 15 enzyme systems, as well as haemoglobin. The frequencies of genes in the ABO, MN and Rh blood group systems are compatible with values reported previouslythe fourth blood group system Ina was invariant, all persons tested being In(a-). Similarly no variants were detected in the transferrin, caeruloplasmin and albumin serum protein systerns. The haptoglobin gene Hp1 had a frequency of 0.41, high for Indian populations and also the Gm-1–2allele had a high frequency. Two individuals had the rare phenotype Gm (–1, +2). Amongst the red cell enzyme systems distinctive variants were detected in the phospho-gluconate dehydrogenase, phosphoglucomutase (locus 1) and peptidase B systems. The allele PGDKadar controls an electrophoretically fast variant and examples of combinations of this allele with PGDA, PGDC and itself were observed. In the PGM (locus 1) system an allele controlling a slower than normal component was present and may be identical with the PGD61 (African) allele detected in a black African. Individuals homozygous for this allele and others heterozygous with it and the normal PGM11and PGM12alleles were present. A single person with a peptidase B variant was detected. The mobility of the variant band was indistinguishable from the Pep B 6 in Australian aboriginals. The pb allele of the acid phosphatase system accounted for nearly 90%, Calcutta-1 variants had a frequency of 3.3%, the AK2 gene frequency was only 3.3%, and only two cases of HbS were detected. All other systems were invariant. Theories concerning the origin of the possible negrito-like traits in a small number of Kadar were discussed and the present evidence was considered to support the possibility of past African negro admixture on a small scale. The postulated genetic reconstruction of the ancestral Kadar population suggests that they may have been similar to Melanesian and Australian aboriginal populations, but that this original genetic structure has been modified through incorporating genetic elements not only from black Africans but from surrounding Dravidian populations.
The codon 31 polymorphism of the p53-inducible protein p21 was studied with respect to allele frequency variations between some major ethnic groups. The frequency of the A1 (Arg) allele showed highly significant variations ranging from 4% in Caucasians (Swedes) to 50% in Chinese. Compared to Caucasians, a relatively high frequency was found in African Blacks (29%) and Indians (16%). Furthermore, Finns and Mordvinians also had higher frequencies (9–10%) than west Europeans (French and Swedes), consistent with an Asiatic Mongoloid influence known to exist in Finno-Ugrian tribes. The geographic allele frequency patterns of p53 and its effector protein p21 were quite different. The p21 A1 mutations in African, Asiatic and European populations were identical at the DNA level. The geographical distribution of the A1 allele suggests an independent origin in Africa and Asia. The very pronounced ethnic differentiation of tumour suppressor genes and the fact that tumour suppressor genes may be teratogenes suggest that these polymorphisms are maintained by natural selection, probably operating in the intrauterine period.
233 Pushtoons (129 males and 104 females), 51 Punjabi Muslims (29 males and 22 females) and 21 Afghans (15 males and 6 females) were screened for the presence of red cell glucose-6-phosphate dehydrogenase (G6PD) variants by a dye decolouration screening test and starch gel electrophoresis. The overall frequency of G6PD deficiency in males was found to be about 10%. 17 male G6PD-deficient samples were further investigated for the C→T substitution at nucleotide (nt) 563 (the Mediterranean mutation) and the C→T substitution at nt 1311 (the ‘silent’ allele) of the G6PD gene by PCR amplification followed by digestion with appropriate restriction enzymes. 10 of the 13 Pushtoon, 2 Punjabi and 1 Afghan males had the 563 mutations. Only 1 (Punjabi) out of 13 G6PD-deficient males with the 563 mutation had the silent mutation at nt 1311. The frequency of the silent mutation was found to be about 0.20 in the 60 Pushtoon and 19 Punjabi non-deficient males.
1. An electrophoretic system in which N-acetyl hexosaminidase C (HEX(C)) MIGRATES LESS ANODALLY THAN N-acetyl hexosaminidase A (HEX(A)) is described. 2. HEX(C) is shown to differ from HEX(A) and HEX(B) in substrate specificity, molecular size and affinity for Concanavalin-A. 3. HEX(C) is present in a wide range of adult and foetal tissues and in tissues from patients with Tay-Sachs and Sandhoff's diseases. It is particularly prominent in brain, testis, thymus and lymphoblastoid cell extracts and in several foetal tissues. 4. It is suggested that HEX(C) is coded at a separate gene locus from HEX(A) and HEX(B).
The distribution of the adult lactase phenotypes, lactose absorption, and lactose malabsorption, was determined by a field version of the hydrogen breath test for disaccharide absorption in a sample of 563 subjects residing in the Democratic Republic of the Sudan. Relatively high proportions of lactose absorption were found in the northern nomadic groups who rely heavily on dairying for their livelihood. Residential Nile valley populations revealed intermediate frequencies of the two phenotypes whereas the negroid populations of the south exhibited a high prevalence of lactose malabsorption irrespective of their economic status with respect to agriculture and dairying. The frequency of the "hypolactasia allele" ranged between 0.6 and 0.87 in the major regional groups.
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