Polymorphic analysis of hypervariable mimisatellite related to recombination hot spot

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Human tandem repeats account for about 3% of the human genome and (excluding satellite DNA) are classified into two groups according to the size of the repeat unit and the overall length of the repeat array. Human minisatellites or variable number tandem repeat (VNTR) loci have repeat units from 6 bp to more than 100 bp long depending on the locus, with arrays usually kilobases in length. Human GC-rich minisatellites are preferentially found clustered in the recombination-proficient subtelomeric regions of chromosomes. Some minisatellite loci show very high levels of allele length variability.Most minisatellite loci consist of heterogeneous arrays of two or more subtly different repeat unit types (minisatellite variant repeats). All human hypervariable minisatellites characterized to date vary not only in repeat copy number (allele length) but also in the interspersion pattern of these variant repeat units within the array. This internal variation provides a powerful approach to the st … More udy of allelic variation and processed of mutation. Interspersion patterns can be determined by minisatellite variant repeat (MVR) mapping and reveals far more variability than can be resolved by allele length analysis.We analyse minisatellite B6,7 locus in the Japanese population. Allele size distributions showed that Japanese retain extensive allele length variability but have significantly smaller alleles compared to north Europeans. Ninety-two Japanese alleles were further characterised by MVR-PCR. These alleles showed a wide variety of internal MVR structures with most alleles observed only once in the sample. The true heterozygosity is estimated at 99.95%, with well in express of 2000 different alleles existing in the Japanese population. Dot matrix analysis showed that groups of related alleles sharing structural motifs could be identified within Japanese and in north Europeans, and that these groups are population-specific with no examples of significant similarity between any Japanese and north European alleles. Minisatellite B6.7 therefore shows huge allele variability and fast repeat turnover in Japanese as well as north European populations, and provide novel lineage markers for exploring very recent events in human population history.We also anlaysed the properties of another hypervariable minisatellite CEB1 (D2S90) in the Japanese population. The length heterozygosity is observed at 85.0% and the average length of the alleles is 69 repeats. A new single nucleotide polymorphism (SMP) was found in the flanking the minisatellite. Internal MVR structure was different between alleles and new vase substitutions/deletions were found within repeats, which indicates CEB1 is also one of the most hypervariable minisatellite loci in Japanese. Less