A search for human Y-chromosome-specific minisatellites and microsatellites

• Main Author: Fretwell, Neale
• Published: University of Leicester 1996
• Subjects: 576.5
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.674465

This thesis describes an attempt to isolate polymorphic minisatellite and microsatellite loci from the male-specific region of the human Y chromosome. Y chromosome polymorphisms are useful in the study of human evolution, since the majority of the chromosome is exempt from meiotic recombination and is passed down intact in paternal lineages. Y-specific polymorphisms can be used to identify males that are related by descent. Base substitutions and sequence insertions are ideal for such analysis, because they represent very rare events and are unlikely to recur. However, these mutations are often highly population-specific, making them of little use in the investigation of inter-population relationships, or of intra-population studies in many cases. Minisatellite and microsatellite loci, on the other hand, show variability in all populations and complement the 'unique event' markers. A systematic search of a human Y-specific cosmid library for G+C-rich minisatellites identified many repetitive sequences, including 14 minisatellites from the Yp pseudoautosomal region. However no Y-specific minisatellites were found. Such sequences must be very rare, and may not be present at all in the Y-specific euchromatin, perhaps because inter-allelic exchange events are precluded in this region. Six novel Y-specific microsatellites were cloned using hybridisation selection from a degenerate PCR library. One multi-locus and two single-locus trinucleotide microsatellites were shown to be polymorphic and were used with two other microsatellites in a survey of diversity in 340 males, and to investigate the relationships between males in different haplotypic groups. No evidence for increased African diversity of Y chromosomes was found in an intercontinental comparison. These markers were also used to classify deletion and duplication events at the 50f2/C locus in 66 males from various populations. This analysis allowed the identification of novel deletion events that had not been distinguished by previous haplotyping analysis with base substitution and other polymorphisms.