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 In^a 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 PGD^Kadar controls an electrophoretically fast variant and examples of combinations of this allele with PGD^A, PGD^C 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 p^b 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.

Previous reports of preferential transmission of bipolar affective disorder (BP) from the maternal versus the paternal lines in families suggested that this disorder may be caused by mitochondrial DNA mutations. We have sequenced the mitochondrial genome in 25 BP patients with family histories of psychiatric disorder that suggest matrilineal inheritance. No polymorphism identified more than once in this sequencing showed any significant association with BP in association studies using 94 cases and 94 controls. To determine whether our BP sample showed evidence of selection against the maternal lineage, we determined genetic distances between all possible pairwise comparisons within the BP and control groups, based on multilocus mitochondrial polymorphism haplotypes. These analyses revealed fewer closely related haplotypes in the BP group than in the matched control group, suggesting selection against maternal lineages in this disease. Such selection is compatible with recurrent mitochondrial mutations, which are associated with slightly decreased fitness. Although such mismatch distribution comparisons have been used previously for analyses of population histories, this is, as far as we are aware, the first report of this method being used to study disease.

A total of nearly 1,000 persons belonging to a number of caste, religious and tribal groupings in Kerala and the Nilgiri Hills of South India have been tested for genetic variation in 4 blood group, 5 serum protein and 17 enzyme systems as well as haemoglobin. The distribution of blood groups, serum protein and enzyme groups is similar to that reported for other South Indian populations. Of particular interest is the presence of LDH ‘Calcutta-1 variants in three of the Hindu and Muslim communities, as well as in two of the tribal populations. At locus 1 of phosphoglucomutase a new allele of the ‘slow’ variety was detected in more than 10% of the Malayarayan, in Kerala, but no examples of this variant were found in neighbouring populations. Abnormal haemoglobins were detected in several populations, HbS being present in more than 20% of the Irula and Kurumba in the Nilgiri Hills. In the Kerala populations there were 4 examples of Hb AD and 1 of Hb AE. Genetic distance estimates using the gene frequency data indicate that the closest groups are the Nayar and Izhava and the Brahmin and Nayar. The tribal populations are approximately twice as far from the Nayar as they are from the Izhava. The Todas of the Nilgiri Hills are somewhat closer to the Brahmin of Kerala than they are to the other tribal populations.

Transferrin subtypes have been determined by isoelectric focussing of sera from 3,787 individuals in selected populations in the Asian, Pacific and Australian area. Tf^C1and Tf^C2were present in all populations studied. Tf^C3 was found to be polymorphic in a few populations only. The highest frequency of Tf^C2was found in the Soliga (34%), an Indian tribal population, and the lowest Tf^C2 safrequency was in Australian Aborigines (3%). In Pacific island populations Tf^C2was found to be variable between 4 and 22%. A new subtype allele, Tf^C6, was observed at polymorphic frequency in Australian Aborigines.

A population genetic study among the Kota of the Nilgiri Hills, South India, involved tests for abnormal haemoglobins, 5 red cell antigen systems, 4 serum protein and 13 red cell enzyme systems. Twelve systems are invariant in the Kota. The most distinctive characteristics are extremely low frequency of the A₁gene and complete absence of A₂in the ABO system, r(cde) in the Rh system, LDH^Cal-1among the enzyme systems as well as absence of abnormal haemoglobins. A comparison of gene frequencies in those systems, which show variation, suggests that the Kota are more similar to the Toda than to any other tribal or caste population of the area. Genetic distance as well as principal component analysis also reveals that the Toda and Kota are close to each other, in agreement with tradition.