Categories Anthropology I

I.9.6 Age, sex and population variation as genetic marker- blood enzymes

Diversity in Human Populations

In acid phosphatase locus 1 system, like other world populations, in Indian populations the ACP1*B allele is preponderant (0.756), followed by ACP1*A (0.242) while the third allele of the system ACP1*C has a trace frequency (0.002).
The average frequency of ACP1*A allele in people of India is 0.242, ranging from 0.035 to 0.467. The distribution of this red cell enzyme polymorphism in five geographical regions of the country i.e. North, West, Central, East and South India was studied by Chahal et al. (1985) who observed that the populations of North India are characterized by relatively high frequencies of ACP1*A and ACP1*C, which differentiate them from populations of all other regions. It was also observed that the incidence of both these alleles is generally higher in the non-tribal populations compared to the tribals of India. Indeed, as stated by Roberts et al. (1980) “the distribution of ACP1*C is essentially non-tribal in India.”

In red cell enzyme phosphoglucomutase locus 1 polymorphism, the average frequency of PGM1*2 is 0.300 in Indian populations, varying from 0.05 in Chaudhuri of West India to 0.558 in Kurumba of South India. In populations with Mongoloid affinities inhabiting Eastern Himalayas the frequency of the allele is somewhat higher (0.309) compared to those of South India (0.298). In general, the frequency of PGM1*2 is low in North India and it gradually starts increasing in West and East India while it decreases in East, Central and South India.

In adenylate kinase locus 1 polymorphism, the average frequency of AK1*2 in Indian populations is is 0.076 with a range of nil to 0.205. The frequency of the allele is low in the people of Himalayas having varying degrees of Mongoloid admixture (0.058) but in populations of the peninsular (South) India it is comparatively high (0.082). Chahal et al. (1986a) studied the distribution pattern of this red cell enzyme polymorphism in the five geographical regions of India and found that there is a clear distinction between non-tribal (range 0.086-0.099) and tribal (range 0.042-0.064) populations inhabiting these regions. Thus tribal populations of India are characterized by having comparatively much lower AK1*2 frequency.

In red cell enzyme adenosine deaminase system, the average frequency of ADA*2 is 0.118 in various populations of India, varying from 0.015 in Jalari of Andhra Pradesh to 0.5 in Muslims and Kacharis of Assam. However, most of the Indian populations fall in a range of 0.015 – 0.214 for this allele. The frequency of the allele is quite low in the populations with Mongoloid ethnicity inhabiting Himalayas (0.087), followed by the peninsular populations of South India with Australoid (Pre-Dravidian) and Caucasoid (Dravidian) racial affinities compared to people of Indus-Ganga-Brahmaputra plains of North India with Caucasoid (Aryan) affinities (0.151).

In esterase D system, the average frequency of ESD*2 in India is 0.271, ranging from as low as 0.022 in Gaddi of Kangra in Himachal Pradesh to 0.582 in people of Andhra Pradesh. The frequency is low in people of Himalayas (0.253) and Indus-Ganga-Brahmaputra plains (0.256) while it is comparatively higher in that of peninsular India (0.322). In fact, there exists a north-south cline of increasing ESD*2 frequency in this red cell enzyme polymorphism in India (Chahal et al., 1986b).

The data on red cell enzyme glyoxalase I polymorphism in Indian populations are rather limited, especially among tribals. Apparently there are no great differences in GLO1*1 frequency in them. The frequency of GLO1*1 ranges from about 0.2 to 0.3 in most of them. Chahal et al. (1986) found somewhat elevated frequenciy of the allele in people of West India and attributed it mainly to the inclusion of two immigrant populations of the Parsi and Irani.

In red cell enzyme glucose phosphate isomerase (phosphohexose isomerase) system the frequency of the GPI*1 allele is unity in most world populations, except Asiatic Indians and Japanese in which rare alleles, respectively, GPI*3 and GPI*4 are present. Various Indian populations have been screened for variants of GPI (Papiha and Chahal, 1984) and the rare allele GPI*3 attain polymorphic proportions in many of them. With a frequency as high as 0.110 of the allele, the Bhotia of Chamoli district in Garhwal region of Uttarakhand stand out from all populations of India (Chahal et al., 2008). In addition to GPI*3, other variant alleles reported from the country include GPI*2, GPI*4, GPI*5, GPI*7, GPI*8 and GPI*9, albeit some of them are limited to specific ethnic groups or geographical regions.

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