An extremely polymorphic locus on the short arm of the human X chromosome with homology to the long arm of the Y chromosome.
A genomic DNA clone named CRI-S232 reveals an array of highly polymorphic restriction fragments on the X chromosome as well as a set of non-polymorphic fragments on the Y chromosome. Every individual has multiple bands, highly variable in length, in every restriction enzyme digest tested. One set of bands is found in all males, and co-segregates with the Y chromosome in families. These sequences have been regionally localized by deletion mapping to the long arm of the Y chromosome. Segregation analysis in families shows that all of the remaining fragments co-segregate as a single locus on the X chromosome, each haplotype consisting of three or more polymorphic fragments. This locus (designated DXS278) is linked to several markers on Xp, the closest being dic56 (DXS143) at a distance of 2 cM. Although it is outside the pseudoautosomal region, the S232 X chromosome locus shows linkage to pseudoautosomal markers in female meiosis. In determining the X chromosome S232 haplotypes of 138 offspring among 19 families, we observed three non-parental haplotypes. Two were recombinant haplotypes, consistent with a cross-over among the S232-hybridizing fragments in maternal meiosis. The third was a mutant haplotype arising on a paternal X chromosome. The locus identified by CRI-S232 may therefore be a recombination and mutation hotspot.
Knowlton
R G
RG
Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, PA 19107.
Nelson
C A
CA
Brown
V A
VA
Page
D C
DC
Donis-Keller
H
H
D002460:Cell Line; D002874:Chromosome Mapping; D002897:Chromosomes, Human, Pair 7; D003001:Cloning, Molecular; D005260:Female; D008040:Genetic Linkage; D006801:Humans; D008297:Male; D009693:Nucleic Acid Hybridization; D010375:Pedigree; D011110:Polymorphism, Genetic; D012689:Sequence Homology, Nucleic Acid; D014960:X Chromosome; D014998:Y Chromosome