Genetic variation in Arizona Mexican Americans: estimation and interpretation of admixture proportions.
Mexican Americans are a numerous and fast growing ethnic population in the United States. Yet little is known about their genetic structure. Since they are a hybrid, it is of interest to identify their parental populations and to estimate the relative contributions of these groups. This information is relevant to historical, biomedical, and evolutionary concerns. New genetic typings on 730 Arizona Mexican Americans for the HLA-A, HLA-B, ABO, Rh, MNSs, Duffy, Kidd, and Kell loci are presented here and they are used to estimate ancestral contributions. We considered both a dihybrid model with Amerindians and Spaniards as proposed ancestors, and a trihybrid model with Amerindians, Spaniards, and Africans as proposed ancestors. A modified weighted least squares method that allows for linkage disequilibrium was used to estimate ancestral contributions for each model. The following admixture estimates were obtained: Amerindian, 0.29 +/- 0.04; Spaniard, 0.68 +/- 0.05; and African, 0.03 +/- 0.02. The interpretation of these results with respect to Amerindian and Spanish ancestry is straightforward. African ancestry is strongly supported by the presence of a marker of African descent, Fy, despite the fact that the standard error of the estimate is as large as the estimated admixture proportion. An evaluation of the sensitivity of these results to a number of variables is presented: 1) our choices of ancestral allele frequencies, 2) the possibility of selection at HLA and the blood groups, and 3) genetic drift in Mexican Americans.
Long
J C
JC
Department of Anthropology, University of New Mexico, Albuquerque 87131.
Williams
R C
RC
McAuley
J E
JE
Medis
R
R
Partel
R
R
Tregellas
W M
WM
South
S F
SF
Rea
A E
AE
McCormick
S B
SB
Iwaniec
U
U
D000349:Africa / Q000208:ethnology; D000483:Alleles; D001130:Arizona; D044383:Black People / Q000235:genetics; D001789:Blood Group Antigens / Q000235:genetics; D001788:Blood Grouping and Crossmatching; D005260:Female; D005787:Gene Frequency; D014644:Genetic Variation; D006680:HLA Antigens / Q000235:genetics; D006630:Hispanic or Latino / Q000235:genetics*; D006801:Humans; D007198:Indians, North American / Q000235:genetics*; D008297:Male; D008800:Mexico / Q000208:ethnology; D013030:Spain / Q000208:ethnology; D044465:White People / Q000235:genetics; D001741:Black or African American
D001789:Blood Group Antigens; D006680:HLA Antigens