title: X-chromosomal genetic diversity and linkage disequilibrium patterns in Amerindians and non-Amerindian populations.
abstract: OBJECTIVE
  We report X-chromosomal linkage disequilibrium (LD) patterns in Amerindian (Kogi, Wayuu, and Zenu) and admixed Latin American (Central Valley of Costa Rica and Southern Brazilian Gaucho) populations.
  
  
  METHODS
  Short tandem repeats (STRs) widespread along the X-chromosome were investigated in 132 and 124 chromosomes sampled from the Amerindian tribes and the admixed Latin American populations, respectively. Diversity indexes (gene diversity and average numbers of alleles per locus) were estimated for each population and the level of LD was inferred with an exact test.
  
  
  RESULTS
  The Amerindian populations presented lower genetic diversity and a higher proportion of loci in LD than the admixed ones. Two haplotype blocks were identified in the X-chromosome, both restricted to the Amerindians. The first involved DXS8051 and DXS7108 in Xp22.22 and Xp22.3, while the second found only among the Kogi, included eight loci in a region between Xp11.4 and Xq21.1.
  
  
  CONCLUSIONS
  In accordance to previous work done with other populations, human isolates, such as Amerindian tribes, seem to be an optimal choice for the implementation of association studies due to the wide extent of LD which can be found in their gene pool. On the other hand, the low proportion of loci in LD found in both admixed populations studied here could be explained by events related to their history and similarities between the allele frequencies in the parental stocks.
authors.affiliation: Programa de Pós-Graduação em Genética e Biologia Molecular and Departamento de Genética, Instituto de Biociências, Universidade Federal do Rio Grande do Sul, Caixa Postal 15053, 91501-970, Porto Alegre, RS, Brazil.
authors.forename: Carlos Eduardo G
authors.initials: CE
authors.lastname: Amorim
authors.forename: Sijia
authors.initials: S
authors.lastname: Wang
authors.forename: Andrea R
authors.initials: AR
authors.lastname: Marrero
authors.forename: Francisco M
authors.initials: FM
authors.lastname: Salzano
authors.forename: Andrés
authors.initials: A
authors.lastname: Ruiz-Linares
authors.forename: Maria Cátira
authors.initials: MC
authors.lastname: Bortolini
mesh_terms: D001938:Brazil; D041321:Chromosomes, Human, X / Q000235:genetics*; D003105:Colombia; D003364:Costa Rica; D005260:Female; D005787:Gene Frequency; D014644:Genetic Variation; D006239:Haplotypes; D006801:Humans; D007197:Indians, Central American / Q000235:genetics*; D007199:Indians, South American / Q000235:genetics*; D015810:Linkage Disequilibrium; D008297:Male; D018895:Microsatellite Repeats; D044465:White People / Q000235:genetics*