An anthropobiological study in Basse Kotto (Central Africa). I. Erythrocyte and sero-genetic markers An analysis of the genetic differentiationкод для вставкиСкачать
AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 6039-47 11983) An Anthropobiological Study in Basse Kotto (Central Africa). I. Erythrocyte and Sero-genetic Markers: An Analysis of the Genetic Differentiation GABRIELLA SPEDINI, HUBERT WALTER, ENRICO CAPUCCI, MARIA FUCIARELLI, OLGA RICKARDS, MARIA LUISA AEBISCHER, AND NICOLETTA CROSTI Institute ofAnthropology, Uniuersity of Rome, Rome, Italy (G.S., E. C., M . R , 0.R.1; Department of BiologpHuman Biology/Physical Anthropology, University o f Bremen, Bremen, Federal Republic o f Germany (HW); National Centre ofBlood Transfusion of the Italian Red Cross, Rome, Italy (M.L.A.); and Institute of Human Genetics, Catholic Uniuersity, School of Medicine, Rome, ftaly IN C.) KEY WORDS Central Africa, Mbugu, Yakpa, Sango, Erythrocyte polymorphisms, Serum polymorphisms, Genetic heterogeneity, Genetic distances ABSTRACT Phenotype and allele frequencies for hemoglobin types (Hbp), acid phosphatase (AcP), phosphoglucomutase (PGM1 and PGMz), esterase D (EsD), 6-phosphogluconate dehydrogenase (6-PGD), glyoxalase I (GLO), superoxide dismutase (SOD A), and adenylate kinase (AK) as well as for haptoglobins (Hp), group-specific component (Gc),transferrin (M,Gm, and Inv groups and albumin, are reported in the Mbugu, Sango, Yakpa, and Baya Mandja ethnic groups in the Basse Kotto district of the Central African Republic. The total sample size amounts to 133 males and 128 females aged from 16 to 60, unrelated and healthy. A new albumin variant (albumin Mbugu) is described and discussed. The average heterozygosity is high in each group because of a high degree of exogamy. The FSTaverage standardized value among the four groups indicates that the genetic differentiation in Basse Kotto is at level of about 2 4 . This indicates that the four examined groups might be considered genetically homogeneous, in spite of their different ethnic origins. The genetic distances among the four groups show that only the Baya Mandja are less closely related to the other three groups because of their foreign origin. The district of Basse Kotto, Central African Republic, where the present survey was carried out, is included in the southern area of Central Ubangui, which consists of a n undulating plateau at 600 m above sea level from 4" to 6" latitude N and from 20" to 22" longitude E. To the east, the Lower Kotto River fixes the boundary with the district of Mboumu, and southwards the plateau slopes down to the right bank of the Middle Ubangui rather roughly. For most of its length the river marks the boundary between the Central African Republic and Zaire (Fig. 1). The plateau is crossed by a track that links Bangui, the capital of Central Africa, with Bangassou. This track winds for a total of 650 km along the shrubby savanna, alternating wide strips of gallery forests along the water courses with coffee and tobacco plantations and with cotton, sesame, and peanut 0002-948318316001-0039$03.00C2 1983 ALAN R. LISS, INC. plantations particularly in Basse Kotto. During the rainy season (from March to October) this track is impassable for' long distances, causing connections between the western and eastern areas of the country to become very difficult, and trade activities, particularly retail, to be greatly curtailed, just because of the poor state of the roads. The main economic source for a family is represented by the work which the active male population carries out either directly in the plantations or in the factories connected to them (i.e., in the important oil mill at Alindao). Women attend to the cultivation of vegetables. On the plateau, along the track, hamlets of typical Sudanic houses (circular huts with Received January 4,1982; accepted April 15,1982 40 G. SPEDINI ET AL. -~ THE CENTRAL AFRICAN *m. 30 D 80 _ - - , m Do 15 120 REP Irn rra V 16. 011 1 I 2 0. Lp--2 2 2. 1= NZAKARA Fig. 1. Geographic location of the four considered ethnic groups. conical roofs) follow one another close to the savanna. However, these villages are not permanent. One often sees the carbonized ruins of complete villages along the track, because the villagers set fire to the savanna during the dry season in order to flush small game. The energy intake is generally sufficient; in fact, it covers 98% of the total needs, especially carbohydrates (manioc and maize). In contrast, lipid intake is low (40 g per capitdday) and proteins amount to less than 50 g per capitdday (O.M.S., 1977). Children often show clear signs of protein malnutrition, with frequent avitaminosis (riboflavin, thiamine, vitamin A) (Cresta, 1965). The nutrition situation is made more precarious by various dietary taboos that are particularly in force in the most vulnerable population: children and pregnant women (e.g., among the Banda, eggs and fish are forbidden to them because “these foods produce skin spots and children’s caries”). The hygienic and sanitary situation is also very poor; the child mortality rate is close to 19%(demographic inquiry in 1959).The more frequent causes of death are the anemias associated with malnutrition and parasites, primarily malaria and the genetic hemoglobinopathies; 26%of deaths in the first year of life and 13% from 1 to 4 years are due to malnutrition (compared to 11%found at the Civil Hospital of the capital city, Bangui). Goiter is also frequent; Cresta (1965) found that about 19% of 450 Banda adults were suffering from adenomatous goiter and about 7% from visible goiter. In central Ubangui, the district of Basse Kotto is inhabited by two main ethnic groups: the Banda, settled more in the interior, and the Ngbandi-Yakoma, along the sandbanks of the upper and middIe Ubangui River. The GENETIC DIFFERENTIATION IN CENTRAL AFRICA Banda belong to the equatorial branch of the eastern Nigritic peoples (Murdock, 1959). They reached Central Ubangui in about the 19th century, when some Sudanic groups were forced to cross the Bahr el Ghaza to escape Nubian and Arab slave raids, separating into various small groups and settling in a large area including from 4" latitude N and from 16" to 25" longitude E. They did not reach the Ubangui River banks, however, because the Ngbandi-Yakoma populations, already settled, prevented them. A t present the Banda represent 53%of the Central Ubangui population. The social structure is based on clans, each clan consisting of several families with a polygamous chief. Because of their settlement in different geographic areas, the Banda cannot be considered an homogeneous unit. Within the subdivided groups endogamy is not observed. About 77% of marriageable females (45% marry at age 14-20 years) are chosen outside of the husband's village of residence, but inside the Banda area. Exogamy is more common among the Ngbandi-Yakoma, more than 78% of the females coming from Yakoma villages other than the husband's. In addition, no less than 54% of males over 15 years come not only from villages on the right (Central African Republic), but also on the left bank (Zaire) of the Ubangui River. All of that shows the great mobility inside the group. However, the environmental conditions connected with the great river and the language tend to preserve the groups' cultural homogeneity. A t present they amount to about 20,000 individuals; they border eastward on the N'Zakara and the Azande. The Banda tribes, settled in Basse Kotto, are the Langba, the Dakpa, the Yakpa, and some smaller ones. Girard (1901) and Daigre (1947) count the Mbugu among the Banda. According to Murdock (1959) and Biasutti (1967), however, they do not belong to the same stock, being a residual group of a tribe that belongs to the southern branch of the Cushitic subfamily. The Ngbandi-Yakoma tribes of the same area include the Sango and Banziri. Owing to the uncertain position of the Mbugu, we have compared them with the Yakpa (Banda) and Sango (Ngbandi-Yakoma) either as to their morphometric traits or as to the distribution of several genetic markers. MATERIALS AND METHODS The Basse Kotto survey was carried out in January 1979 (Spedini) in the villages of 41 Kongbo (4"33' latitude N, 660 km east of Bangui) and of Mobaye (4'22' latitude N, 60 km south of Kongbo), an important center built on the banks of the Ubangui River (Laurentin-Retel, 19791, and in November of the same year (Spedini and Capucci) in Mobaye. The sample reported consists of 133 males and 128 females 16 to 60 years, unrelated and healthy, and a group of 77 infants less than 2 years. Body measurements, finger and palmar dermatoglyphics, and blood were obtained in the Dispensary of the Swiss Evangelic Mission at Elime (4 km from Kongbo) and in the hospital a t Mobaye. Venous blood was collected in ACD and stored a t about 0°C both during transportation to Bangui and shipment by air to Rome. A portion of the whole-blood sample was utilized, within 2 weeks, for typing blood groups as ABO, MNSs, Rh (-C, -c, -D, -E, -e), and Duffy in the National Centre of Blood Transfusion (NCBT)of the Italian Red Cross, Rome. Hemolysate and plasma samples, divided into 1-2 cc aliquots, were stored a t -20°C until used. In the same center, triiodothyroxine (T3), thyroxine (T& and thyrotropin (TSH) hormone levels and analysis for HbsAg typing by radioimmunological techniques were carried out, and Treponema pallidurn was shown by VDRL test. In the Laboratory of the Institute of Anthropology, University of Rome, Hb types, serum proteins, and serum lipids were detected by electrophoresis, using cellogel strips, according to Helena Laboratories (Beaumont, Texas), The total levels of serum proteins, serum lipids, cholesterol, and hemoglobin were determined using Boehringer kits and a Bausch and Lomb spectrophotometer. The electrophoretic support for the determination of the erythrocyte enzyme polymorphisms acid phosphatase (AcP),phosphoglucomutase (PGMI and PGMZ), adenylate kinase (AK), 6phosphogluconate dehydrogenase (6-PGD), and esterase D (EsD) was cellogel RS and the staining was carried out by the method of Chemetron (Milan). The electrophoretic support for determination of haptoglobin types (Hp) was cyanogum (Hoppe et al., 1972; modified). In a few cases, for further verification, electrophoresis on starch gel, according to Karp and Sutton (1967), for the RA and RB phenotypes was utilized. In the Institute of Human Genetics (Sacred Heart University, Rome) glyoxalase I (GLO) and superoxide dismutase (SOD A) were de- 42 G.SPEDINI ET AL. tected using as support cellogel RS (MeeraKhan and Doppert, 1976; Chemetron, Milan, respectively), and in a few cases, for further verification, according to Crosti et al. (1976); the support for transferrin types (TO was cyanogum (Matson et al., 1965). Finally, Gm and Inv (Km) groups and Gc types were determined in the Laboratory of Human Biology, Department of Biology, University of Bremen (West Germany). Data on blood group polymorphisms (ABO, MNSs, Rh, and Duffy), hemoglobin types, and HBsAg have been reported (Spedini et al., 1981; Capucci et al. 1980-81b) as those regarding some anthropometric variables Capucci et al., 1980-81a), a partial sample for the AcP system (Spedini et al., 19801, and GLO and SOD A polymorphisms (Spedini et al., 1982). The dermatoglyphics analysis is in progress. In this paper we report AcP, PGMl, AK, 6PDG, Hp, Gc, Tf, Gm, and Inv frequencies. We have been able to analyze blood samples of 139 unrelated Mbugu, 34 Yakpa, 73 Sango, and 15 Baya Mandja. This last sample has been included in spite of its small number because until now no data have been available. The Baya Mandja are aliens to the territory of Basse Kotto; they represent about 15% of the entire population of Central Africa, and occupy the region to the west from north to south, and the comparison with the local groups of Basse Kotto could give some interesting indications about the eventual contribution of the actual genetic structure of that territory. RESULTS AND DISCUSSION Phenotype and gene frequencies are shown in Table 1for the red cell enzyme polymorphisms AcP, PGMI, EsD, 6-PGD, and GLO as well as for Hbp variability and for the serum polymorphisms Hp and Inv. No variation was found in any group in the PGMz locus. For the AK locus five Mbugu showed AK 2-1 phenotype (AK1 = 0.9810) and for SOD A locus one Mbugu showed SOD A 2-1 phenotype (SOD A' = 0.9950.) (Another subject, SOD A 2-1, sister of this heterozygote individual, was found). With respect to serum polymorphisms the following results were obtained: Gc locusone Mbugu in a total of 43 subjects and four Sango in a total of 48 subjects showed Gc 2-1 phenotype (Gel = 0.9880 and 0.9580, respectively); Tf locus-three Mbugu out of 44 subjects and one Sango out of 40 subjects showed Tf CD phenotype (Tfc = 0.9660 and 0.9880, respectively). Only one Mbugu out of 45 subjects showed Gm 5, 13 allotype, and another one out of 139 individuals showed an albumin variant. Every locus indicated Hardy-Weinberg equilibrium (for verification we utilized Levene's formula; see Li, 1955).The only exception is that of the Mbugu for the 6-PGD locus (P < 0.0025, 1d.f.1. On the whole, the red cell isoenzymes and hemoglobin allele frequencies observed in Basse Kotto are within the range of those observed in sub-Saharan areas (Spedini et al., 1978). The Hp', Gc', and Tfc allele fre- TABLE 1. Erythrocyte and serum phenotypes and gene frequencies in the Basse Kotto Locus HbR"' Phenotype A AS S Total $1 Mbugu Yakpa Sango Baya 116 14 1 29 5 0 57 16 0 11 0 0 131 0.715 34 0.169 73 1.030 11 0.939 0.061 0.926 0.074 0.890 0.110 I - Gene frequency 8" PS 10 80 37 5 n 1 RB Total $3, 139 6.100 17 10 2 2 5 39 22 1 6 34 1.920 73 1.222 3 1.000 - 1 6 5 0 0 12 0.015 (Table 1 continued on next page) 43 GENETIC DIFFERENTIATION IN CENTRAL AFRICA Locus TABLE 1. Erythrocyte and serum phenotypes and gene frequencies in the Basse Kotto (continued) Phenotype Mbugu Yakpa Sango Baya Gene frequency P 0.223 0.734 0.043 Pb P’ PGMl 1-1 2-1 2-2 Total x:1 I 0.265 0.676 0.059 0.226 0.726 0.048 0.292 0.708 - 8 3 1 113 20 0 24 8 2 53 16 4 133 0.832 34 1.501 73 3.266 12 1.087 0.925 0.075 0.824 0.176 0.836 0.164 0.792 0.208 Gene frequency PGM: PGM? EsD 1-1 2-1 2-2 Total x 6I 105 27 1 25 8 1 60 13 0 11 1 0 133 0.231 34 0.215 73 0.640 12 0.891 0.109 0.853 0.147 0.911 0.089 - Genefre uency EsDsl ESD~ 6-PGD A AC C Total XflI 0.958 0.042 70 3 0 12 0 0 - 73 0.022 12 0.985 0.015 0.979 0.021 125 7 1 33 133 5.845 34 1 0 - Gene frequency PGD* PGD~ ~ ~ 0 ‘ 3 ) 0.966 0.034 1-1 2-1 2-2 Total X;l I 3 8 1.000 - 3 5 7 10 30 52 10 3 27 40 92 2.854 21 0.430 70 0.350 15 1.191 0.333 0.667 0.236 0.764 0.367 0.633 Gene frequency GLO’ GLO~ HP 0.272 0.728 45 50 12 26 1-1 2-1 2-2 0 Total X;l I 4 6 1 1 10 11 5 28 30 3 12 133 0.085 34 0.518 73 1.858 12 0.350 0.654 0.346 0.596 0.404 0.705 0.295 0.636 0.364 16 31 1 8 23 23 2 6 47 9 46 8 0.188 0.057 a Gene frequency ~ ~ “ 4 ) HP2 Inv Inv 1 Inv - 1 Total Gene frequency Inv ~ ~~ “”his figure does not include the sample of 151 boys of Mobaye reported in Spedini et al., 1981. “This figure includes the sample of 90 Mbugu and 50 Sango reported in Spedini et al., 1980. ‘‘’This is the sample of Spedini et al., 1982. ‘‘‘Individuals with Hp 0.0 phenotype were excluded from gene counting. 0.293 0.134 44 G. SPEDINI ET AL quencies are also in good agreement with hitherto published data from the negroids of sub-Saharan Africa. Our average values come to Hpl = 0.65; Tfc = 0.97; Gcl = 0.99 (Mourant et al., 1976: Hpl = 0.28-0.87; Tfc = 0.86-1.00; Gc' = 0.82-0.97). In Basse Kotto, temperature and humidity create excellent conditions for the diffusion of Plasmodium Falciparum. Most likely due to this, HbP5 frequency is 8%, and that of the P" is rather low (about 4%).This figure would confirm the hypothesis suggesting the correlation between a low incidence of this allele and such climatic conditions as are found in sub-Saharan areas. The reason for this correlation may be a selective disadvantage of the P' allele in malaria areas (Spedini et al., 1980). The HbPC allele is absent in Basse Kotto. This is a function of the large geographic distance from the Alto Volta area. Of particular anthropological interest is the presence of a n SOD A 2-1 individual among the Mbugu. This is the first documentation of SOD A2 allele presence in Africa. As gene flow from Caucasoids, in which the frequencies of this allele come to 2% (Welch and Mears, 1972; Beckman and Pakarinen, 1973; Eriksson, 1973; Carter et al., 19761, can be, excluded, the presence of SOD A2 allele in the Mbugu seems most likely to be caused by "an independent mutational event, which occurred in more or less recent times" (Spedini et al., 1982). Of great anthropological interest also is the appearance of a slow-moving albumin variant of the Mexico type (Fig. 2). Unfoi-tunately, it has not been possible to perform a family study to ascertain the genetic nature of this variant, and it has not been possible to get additional samples to confirm this variant by electrophoresis on starch gel. The excellent condition of the sample in question and the fact that the propositus was in good health led us to consider this variant to be a genetic one, which tentatively has been called albumin Mbugu. It seems to be a new variant different from albumin Cayemite, a slow-moving variant, the only one hitherto found in American Negroes (Weitkamp et al., 1969). It should be emphasized that this is the first report on the existence of an albumin variant among African Negroes. Fig. 2. Albumin variant observed in a Mbugu individual. Photograph of cellulose acetate electrophoresis (pH 8.6) (top) and scanned profile (bottom). 45 GENETIC DIFFERENTIATION IN CENTRAL AFRICA Since genetic frequencies reflect exactly the genetic composition of populations, they are the most suitable for population comparisons on a genetics scale. However, before intergroup comparisons, intragroup should be carried out. The simplest and most direct approach for this is the estimation of heterozygosity, considering a s many loci as possible. Since the average heterozygosity (heterogeneity index) of a population is defined not only by interlocus variance (owing to drift), but also by intralocus variance (given that in the multiallelic locus every allele may cause a variation), we have calculated the average heterozygosity for every locus, adopting Nei and Roychoudhury’s (1974a) formula. For each of the groups of Basse Kotto the results obtained are reported in Table 2. Considering the presence of loci at very low heterozygosity or those for which a gene is fixed in the population, as for AK, Gc, Tf loci, it was concluded that the heterozygosity is high in each group. Nevertheless, the small number of individuals in the Yakpa and Baya Mandja groups (less than 50) could affect the sampling variance of heterozygosity (Nei, 1978). In Negroids, Nei and Roychoudhury (1974b) have estimated a n average heterozygosity of 0.162 i 0.035 for 34 blood group loci but only 0.092 k 0.019 considering the enzymatic and nonenzymatic proteins too, for a total of 64 loci. In Basse Kotto, however, considerable heterozygosity within each group exists: about 30% in the Yakpa and Sango and 24% in the Baya Mandja. These results appear congruent with the exogamy practiced in a high degree by the Mbugu and also by the Yakpa of Kongbo, and to a higher degree by the Sango (78%). To estimate the intergroup genetic differentiation we have calculated FST.This was possible by hypothesizing that the high average heterozygosity found in every subpopulation was the result of exogamy, not only among members of a single ethnic group but among members of different groups, so that the effect of the division in ethnic subpopulations would be annulled. In this case too, we have considered that in a multiallelic locus, each allele can produce a different FST and so we have estimated the mean and standard deviations among FSTcoefficients for each locus (Chakraborty et al., 1977; Chakraborty and Ghosh, 1981). The corrected values per allele are given in Table 3. The alleles that contribute most to the total variance are IB,Fya, PGM:, HbPA (about 3-5%), and cDe allotype (about 4%). Thoma (1974) concluded that the IA allele frequency has not reached stability in subSaharan Africa. On the contrary, in Basse Kotto region this allele has reached a considerable stability. This could suggest the presence in the region of a specific selective factor, stabilizing the I* allele. For the Duffy system the greatest variablity of the Fy” allele, in comparison with Fyb and Fy, confirms all TABLE 2. Average heterozygosity per locus Mbugu Sango Yakpa Baya h* vh** h Vh h Vh h Vh 0.005 0.010 0.004 0.0001 0.001 0.002 0.00001 0.00006 0.002 Inv 0.307 0.322 0.710 0.252 0.251 0.000 0.413 0.330 0.080 0.401 0.000 0.463 0.000 0.000 0.232 0.0007 0.017 0.0001 0.0001 0.066 0.461 0.647 0.449 0.334 0.195 0.419 0.275 0.162 0.360 0.000 0.416 0.080 0.025 0.414 0.002 0.009 0.002 0.0001 0.0006 0.001 0.0002 0.001 0.002 Tf 0.003 0.013 0.003 0.0002 0.002 0.001 0.001 0.0004 0.001 0.004 0.002 0.004 0.003 0.0001 0.550 Gc 0.463 0.697 0.472 0.211 0.115 0.410 0.139 0.194 0.395 0.043 0.452 0.023 Locus ABO MNSs Rh Duffy Hbp AcP PGM, EsD GLO AK HP a = 0.285 f 0.003 0.660 0.511 0.239 0.136 0.469 0.291 0.251 0.444 0.000 0.481 0.000 0.000 0.108 0.003 - 0.002 = 0.296 & 0.002 - 0.001 0.003 0.005 0.001 = 0.303 f 0.002 - H - 0.003 0.0008 0.001 0.002 - 0.004 - 0.0005 = 0.245 f 0.001 Note: The average heterozygosity for ABO, MNSs, Rh, and Duffy loci was calculated using the data reported in Spedinl et a]., 1981. 46 G. SPEDINI ET AL. TABLE 3. Heterogeneity o f gene frequencies among four ethnic groups of Basse Kotto lFs7 coefficientl Allele or aplotype I* P 2x 10-3 FST 0.1815 0.1231 0.6954 0.17 4.56 5.01 0.001 0.042 0.024 Ms NS Ns 0.1783 0.3710 0.0760 0.3747 1.06 3.99 5.72 0.50 0.007 0.017 0.008 0.002 CDe cDE cDe cde 0.0373 0.0584 0.7000 0.2043 0.02 0.83 7.12 1.29 0.001 0.015 0.039 0.008 FY” FY Fy 0.0698 0.0714 0.8590 1.88 1.15 0.92 0.029 0.017 0.004 Hb BA 0.9249 1.76 0.0% P“ 0.2325 0.7229 0.0446 0.36 0.36 0.12 0.002 0.002 0.003 0.8790 0.8948 0.7272 0.6610 0.2173 3.67 1.51 1.55 1.69 - 3.56 0.034 0.016 0.008 0.007 0.021 0.003 IB i MS Pb P‘ PGM ESD’ GLO~ HD’ The estimated genetic distances (Nei, 1972), on the other hand, show that the Mbugu are closely related to the Sango and Yakpa but much less to the Baya Mandja (Table 4). This result agrees with the earlier statement that the Baya Mandja represent an ethnic minority of Basse Kotto who recently emigrated from the western regions, their place of origin. ACKNOWLEDGMENTS We wish to thank the staff of the Swiss Evangelic Mission at Elime, and Mr. Mario Ferrari and the missionary sisters of Mobaye for handling the logistics of getting the sample to the Civil Hospital a t Mobaye. We should also like to express our gratitude to the local authorities in making easier the survey and to the people of Mobaye and Kongbo for their cooperation. Finally, we thank Dr. M. E. Danubio and Dr. S. Romagnoli for typing Tf system. LITERATURE CITED Beckman, G, and Pakarinen, A (1973) Superoxide dismutase. A population study. Hum. Hered. 22346-351. Biasatti. R (‘1967)R a z e e Popoli della Terra, Vol. 111. Torino: UTET. In;(l’ Capucci, E, Fuciarelli, M, Rickards, 0, Viscoli, V, and FST = 0.016 Spedini, G (1980-81a) Indagine antropobiologica su alNote: The P values for ABO, MNSs, Rh, and Duffy loci were cune popolazioni del Centro Ubangui (Repubblica Cencalculated using the data reported in Spedini et al., 1981. trafricana). I. Caratteri antropometrici dei Sango, Mbugu e Yakpa. Riv. Antrop. LX1;233-240. Capucci. E, Kickards, 0, Fuciarelli, M, Angcloni, P, AeTABLE 4. Genetic tfistunces aniong fbur ethnic groups bischrr, MI,, Spedini, G 11980-8113) La distribuzione ~Jf’B0,S.W KOfffJ dell’ HBsAg in Africa: Ricerca su alcune popolazioni Yakpa -Sango della “Basse Kotto” (Kepubblica Centrafricana). Riv. _- Mbugu .-~~ -._-~BRya -~ . Antrop. LX1;215-224. Mbugu Carter, ND, Auton, JA, Welch, SG, Marshall, WH, and Yakpa 0.0079 Fraser. GR (1976)Superoxidc dismutase variants In Sango 0.0062 0.0160 Newfoundland: A gene from Scandinavia? Hum. HeBaya 0.0152 0.0210 0.0185 rcd. 26:4-7. Chakraborty, R. Chakravarti. 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