title: Ethnicity and human genetic linkage maps.
abstract: Human genetic linkage maps are based on rates of recombination across the genome. These rates in humans vary by the sex of the parent from whom alleles are inherited, by chromosomal position, and by genomic features, such as GC content and repeat density. We have examined--for the first time, to our knowledge--racial/ethnic differences in genetic maps of humans. We constructed genetic maps based on 353 microsatellite markers in four racial/ethnic groups: whites, African Americans, Mexican Americans, and East Asians (Chinese and Japanese). These maps were generated using 9,291 subjects from 2,900 nuclear families who participated in the National Heart, Lung, and Blood Institute-funded Family Blood Pressure Program, the largest sample used for map construction to date. Although the maps for the different groups are generally similar, we did find regional and genomewide differences across ethnic groups, including a longer genomewide map for African Americans than for other populations. Some of this variation was explained by genotyping artifacts--namely, null alleles (i.e., alleles with null phenotypes) at a number of loci--and by ethnic differences in null-allele frequencies. In particular, null alleles appear to be the likely explanation for the excess map length in African Americans. We also found that nonrandom missing data biases map results. However, we found regions on chromosome 8p and telomeric segments with significant ethnic differences and a suggestive interval on chromosome 12q that were not due to genotype artifacts. The difference on chromosome 8p is likely due to a polymorphic inversion in the region. The results of our investigation have implications for inferences of possible genetic influences on human recombination as well as for future linkage studies, especially those involving populations of nonwhite ethnicity.
authors.affiliation: Department of Genetics, Stanford University, Stanford, CA, USA. jorg@itsa.ucsf.edu
authors.forename: Eric
authors.initials: E
authors.lastname: Jorgenson
authors.forename: Hua
authors.initials: H
authors.lastname: Tang
authors.forename: Maya
authors.initials: M
authors.lastname: Gadde
authors.forename: Mike
authors.initials: M
authors.lastname: Province
authors.forename: Mark
authors.initials: M
authors.lastname: Leppert
authors.forename: Sharon
authors.initials: S
authors.lastname: Kardia
authors.forename: Nicholas
authors.initials: N
authors.lastname: Schork
authors.forename: Richard
authors.initials: R
authors.lastname: Cooper
authors.forename: D C
authors.initials: DC
authors.lastname: Rao
authors.forename: Eric
authors.initials: E
authors.lastname: Boerwinkle
authors.forename: Neil
authors.initials: N
authors.lastname: Risch
mesh_terms: D001741:Black or African American / Q000235:genetics*; D001213:Asian / Q000235:genetics*; D002874:Chromosome Mapping; D002881:Chromosomes, Human, Pair 12 / Q000235:genetics*; D002898:Chromosomes, Human, Pair 8 / Q000235:genetics*; D005260:Female; D005828:Genetics, Population; D005838:Genotype; D006801:Humans; D006973:Hypertension / Q000235:genetics; D008297:Male; D017058:Mexican Americans / Q000235:genetics*; D011110:Polymorphism, Genetic; D014481:United States; D044465:White People / Q000235:genetics*