Am. J. Hum. Genet. 46:776-783, 1990
Five Polymorphic Microsatellite VNTRs on the Human X Chromosome J. A. Luty,* Z. Guo,* H. F. Willardjd D. H. Ledbetter,$ S. Ledbetterj and M. Litt* *Departments of Biochemistry and Medical Genetics, Oregon Health Sciences University. Portland; fDepartment of Medical Genetics, University of Toronto, Toronto; and tinstitute for Molecular Genetics, Baylor College of Medicine, Houston
Summary The human
genome contans approximately 50,000 copies of an interspersed repeat with the sequence (dT.dG/dA.dC)n, where n = ".10-60. We and others have found that several of these repeats have variable lengths in different individuals, with allelic fragments varying in size by multiples of 2 bp. These "microsatellite" variable number of tandem repeats (VNTRs) may be scored by PCR, using unique flanking primers to amplify the repeat-containing regions and resolving the products on DNA sequencing gels. Since few VNTRs have been found on the X chromosome, we screened a flow-sorted X chromosome-specific genomic library for microsatellites. Approximately 25% of the phage clones hybridized to a poly (dTdG).poly(dA-dC) probe. Of seven X-linked microsatellites present in positive phages, five are polymorphic and three have both eight or more alleles and heterozygosities exceeding 75%. Using PCR to amplify genomic DNAs from hybrid cell panels, we confirmed the X localization of these VNTRs and regionally mapped four of them. The fifth VNTR was regionally mapped by virtue of its tight linkage to DXS87 in Centre du Polymorphisme Humain families. We conclude that whatever factors limit the occurrence of "classical" VNTRs and RFLPs on the X chromosome do not appear to operate in the case of microsatellite
VNTRs.
Introduction
It is
Five Polymorphic Microsatellite VNTRs on the Human X Chromosome J. A. Luty,* Z. Guo,* H. F. Willardjd D. H. Ledbetter,$ S. Ledbetterj and M. Litt* *Departments of Biochemistry and Medical Genetics, Oregon Health Sciences University. Portland; fDepartment of Medical Genetics, University of Toronto, Toronto; and tinstitute for Molecular Genetics, Baylor College of Medicine, Houston
Summary The human
genome contans approximately 50,000 copies of an interspersed repeat with the sequence (dT.dG/dA.dC)n, where n = ".10-60. We and others have found that several of these repeats have variable lengths in different individuals, with allelic fragments varying in size by multiples of 2 bp. These "microsatellite" variable number of tandem repeats (VNTRs) may be scored by PCR, using unique flanking primers to amplify the repeat-containing regions and resolving the products on DNA sequencing gels. Since few VNTRs have been found on the X chromosome, we screened a flow-sorted X chromosome-specific genomic library for microsatellites. Approximately 25% of the phage clones hybridized to a poly (dTdG).poly(dA-dC) probe. Of seven X-linked microsatellites present in positive phages, five are polymorphic and three have both eight or more alleles and heterozygosities exceeding 75%. Using PCR to amplify genomic DNAs from hybrid cell panels, we confirmed the X localization of these VNTRs and regionally mapped four of them. The fifth VNTR was regionally mapped by virtue of its tight linkage to DXS87 in Centre du Polymorphisme Humain families. We conclude that whatever factors limit the occurrence of "classical" VNTRs and RFLPs on the X chromosome do not appear to operate in the case of microsatellite
VNTRs.
Introduction
It is
