Genetic relationship of a Mexican Afromestizo population through the analysis of the 3' haplotype of the beta globin gene in betaA chromosomes.

We analyzed 112 beta(A) chromosomes from the Costa Chica region, with the aim of determining the 3' haplotype (3'Hp) in Afromestizo individuals and its relationship with the reported populations. Thirty polymorphic sites were identified by sequencing and two by restriction fragment length polymorphisms. Genetic variability, genetic distances and neutrality tests were performed with the computer program Arlequin 3.0. Three groups were constructed, which we named 3 kb-Hp, 330 bp-Hp and 2.67 kb-Hp with 32, 15 and 17 polymorphic sites respectively. In 3 kb-Hp, 34 different 3' haplotypes (14 of them new) were found; the three most common were 7B1 (17.8%), 7A1 (17.0%) and 1C1 (14.3%). 330 bp-Hp revealed 18 different allelic sequences; the most frequent were the 1 (AT(9)T(5), 22.3%), 2 (AT(8)T(5), 20.5%) and 3 (AT(7)T(7), 20.5%). 2.67 kb-Hp displayed 14 distinct haplotypes, with B1 (30.3%), A1 (28.6%) and C1 (21.4%) having the highest frequencies. The gene diversity of the Costa Chica population was only significantly different to Gambia. In the genetic distances, the p values were not significant for Vanuatu, Sumatra and Central African Republic. The neutrality tests showed that the patterns of diversity in the Costa Chica population deviate significantly from the expectations of the standard neutral model. This is the first work performed in Mexico in which the extended 3'Hp was analyzed in beta(A) chromosomes. The study showed clearly the presence of African and Asian genes in the Costa Chica population.