Minisatellites include some of the most variable loci in the human genome and are superb for diss... more Minisatellites include some of the most variable loci in the human genome and are superb for dissecting processes of tandem repeat DNA instability. Single DNA molecule analysis has revealed different mutation processes operating in the soma and germline. Low-level somatic instability results in simple intra-allelic rearrangements. In contrast, high frequency germline instability involves complex gene conversions and is therefore recombinational in nature, almost certainly occurring at meiosis. To determine whether true meiotic crossovers occur at human minisatellites, we have used polymorphisms near the repeat array to recover recombinant DNA molecules directly from sperm DNA. Analysis of minisatellite MS32 has revealed an intense and highly localised meiotic crossover hotspot centred upstream of the array, the first example of a human hotspot defined at the molecular level. This hotspot extends into the beginning of the repeat array, resulting in unequal and equal crossovers. Array crossovers occur much less frequently than array conversions but appear to arise by a common process, most likely by alternative processing of a recombination initiation complex. The location of MS32 at the boundary of a recombination hotspot suggests that this locus has evolved as a by-product of localised meiotic recombination activity, and that minisatellites might in general mark recombinationally proficient hotspots or hot domains in the genome. Finally, sperm crossover analysis makes it possible to explore the molecular rules that govern human meiotic recombination, and to detect phenomena such as meiotic drive that could provide a possible connection between recombination and DNA sequence diversity itself.
Tandemly repeated DNA is a major component of the human genome, and includes loci contributing to... more Tandemly repeated DNA is a major component of the human genome, and includes loci contributing to human disease. Minisatellites include the most variable human loci described to date, and the mechanisms by which this variation is generated in humans have been studied in detail. Integration of human minisatellites into yeast not only provides a model for further dissecting the molecular basis of length change mutation at these loci, but also more generally allows the study of complex recombinational events in yeast. We have used human minisatellite MS205 integrated into yeast to study the structural details of length change mutations. Apart from showing that mutation at this locus in yeast has features similar to those observed at some minisatellites in humans, including meiosis-specificity, and polarity, in which exchange events are localised to one extremity of the array, we here, for the first time, directly demonstrate that a flanking element in yeast regulates the mutation process. The results therefore support the hypothesis that flanking initiators are involved in minisatellite mutation in humans. Furthermore, mutant alleles showed more complex rearrangements in one orientation than the other. The data also suggest that the mutational pathway for deletions might be different from the pathway generating inter-allelic exchanges and duplications.
Proceedings of The Royal Society of London. Series B, Biological Sciences (1934-1990), 1993
A red kite (Milvus milvus) clone, which cross-hybridizes to a human minisatellite, reveals comple... more A red kite (Milvus milvus) clone, which cross-hybridizes to a human minisatellite, reveals complex polymorphic patterns in members of the Accipitridae, a family of 217 species of birds of prey, which includes the kites, hawks and eagles. The total absence of hybridization to males implies that the sequence is located on the W chromosome, and stable inheritance from mother to daughter suggests that the patterns evolve as haploid matrilines. This has allowed not only the development of a simple and rapid sexing technique but may also provide a means of monitoring matriarchal success and dispersion. As an example, a survey of 36 continental European red kite nests revealed 24 different haplotypes, whereas only 2 were found among 53 Welsh nests. The results show the effect of a dramatic bottleneck in Wales and may provide evidence of recent introgression from the continent.
Proceedings of The Royal Society of London. Series B, Biological Sciences (1934-1990), 1993
The genetic analysis of inbred populations has been facilitated by the development of Variable Nu... more The genetic analysis of inbred populations has been facilitated by the development of Variable Number Tandem Repeat (VNTR) probes. We describe here the first use of a synthetic, concatenated simple sequence probe to detect a single VNTR locus and its use in differentiating populations of the red kite, one of Europe's most threatened birds of prey. Numbering 11000-13000 pairs, this species is patchily distributed, comprising several populations, some of which have recently suffered major bottlenecks. By using the (CCAT)n probe we have examined variation within and among four of these. The levels of heterozygosity and allelic diversity reflect each population's history but also reveal substructuring within the indigenous British population in Wales. Here a group of peripheral territories, which are amongst the most successful in the population, exhibit significantly lower heterozygosity than the main population, and appear to receive little genetic input from it.
Crossover between the human sex chromosomes during male meiosis is restricted to the terminal pse... more Crossover between the human sex chromosomes during male meiosis is restricted to the terminal pseudoautosomal pairing regions. An obligatory exchange occurs in PAR1, an Xp/Yp pseudoautosomal region of 2.6 Mb, which creates a male-specific recombination 'hot domain' with a recombination rate that is about 20 times higher than the genome average. Low-resolution analysis of PAR1 suggests that crossovers are distributed fairly randomly. By contrast, linkage disequilibrium (LD) and sperm crossover analyses indicate that crossovers in autosomal regions tend to cluster into 'hot spots' of 1-2 kb that lie between islands of disequilibrium of tens to hundreds of kilobases. To determine whether at high resolution this autosomal pattern also applies to PAR1, we have examined linkage disequilibrium over an interval of 43 kb around the gene SHOX. Here we show that in northern European populations, disequilibrium decays rapidly with physical distance, which is consistent with this interval of PAR1 being recombinationally active in male meiosis. Analysis of a subregion of 9.9 kb in sperm shows, however, that crossovers are not distributed randomly, but instead cluster into an intense recombination hot spot that is very similar in morphology to autosomal hot spots. Thus, PAR1 crossover activity may be influenced by male-specific hot spots that are highly suitable for characterization by sperm DNA analysis.
Proceedings of The Royal Society of London. Series B, Biological Sciences (1934-1990), 1993
A red kite (Milvus milvus) clone, which cross-hybridizes to a human minisatellite, reveals comple... more A red kite (Milvus milvus) clone, which cross-hybridizes to a human minisatellite, reveals complex polymorphic patterns in members of the Accipitridae, a family of 217 species of birds of prey, which includes the kites, hawks and eagles. The total absence of hybridization to males implies that the sequence is located on the W chromosome, and stable inheritance from mother to daughter suggests that the patterns evolve as haploid matrilines. This has allowed not only the development of a simple and rapid sexing technique but may also provide a means of monitoring matriarchal success and dispersion. As an example, a survey of 36 continental European red kite nests revealed 24 different haplotypes, whereas only 2 were found among 53 Welsh nests. The results show the effect of a dramatic bottleneck in Wales and may provide evidence of recent introgression from the continent.
Minisatellites include some of the most variable loci in the human genome and are superb for diss... more Minisatellites include some of the most variable loci in the human genome and are superb for dissecting processes of tandem repeat DNA instability. Single DNA molecule analysis has revealed different mutation processes operating in the soma and germline. Low-level somatic instability results in simple intra-allelic rearrangements. In contrast, high frequency germline instability involves complex gene conversions and is therefore recombinational in nature, almost certainly occurring at meiosis. To determine whether true meiotic crossovers occur at human minisatellites, we have used polymorphisms near the repeat array to recover recombinant DNA molecules directly from sperm DNA. Analysis of minisatellite MS32 has revealed an intense and highly localised meiotic crossover hotspot centred upstream of the array, the first example of a human hotspot defined at the molecular level. This hotspot extends into the beginning of the repeat array, resulting in unequal and equal crossovers. Array crossovers occur much less frequently than array conversions but appear to arise by a common process, most likely by alternative processing of a recombination initiation complex. The location of MS32 at the boundary of a recombination hotspot suggests that this locus has evolved as a by-product of localised meiotic recombination activity, and that minisatellites might in general mark recombinationally proficient hotspots or hot domains in the genome. Finally, sperm crossover analysis makes it possible to explore the molecular rules that govern human meiotic recombination, and to detect phenomena such as meiotic drive that could provide a possible connection between recombination and DNA sequence diversity itself.
Tandemly repeated DNA is a major component of the human genome, and includes loci contributing to... more Tandemly repeated DNA is a major component of the human genome, and includes loci contributing to human disease. Minisatellites include the most variable human loci described to date, and the mechanisms by which this variation is generated in humans have been studied in detail. Integration of human minisatellites into yeast not only provides a model for further dissecting the molecular basis of length change mutation at these loci, but also more generally allows the study of complex recombinational events in yeast. We have used human minisatellite MS205 integrated into yeast to study the structural details of length change mutations. Apart from showing that mutation at this locus in yeast has features similar to those observed at some minisatellites in humans, including meiosis-specificity, and polarity, in which exchange events are localised to one extremity of the array, we here, for the first time, directly demonstrate that a flanking element in yeast regulates the mutation process. The results therefore support the hypothesis that flanking initiators are involved in minisatellite mutation in humans. Furthermore, mutant alleles showed more complex rearrangements in one orientation than the other. The data also suggest that the mutational pathway for deletions might be different from the pathway generating inter-allelic exchanges and duplications.
Proceedings of The Royal Society of London. Series B, Biological Sciences (1934-1990), 1993
A red kite (Milvus milvus) clone, which cross-hybridizes to a human minisatellite, reveals comple... more A red kite (Milvus milvus) clone, which cross-hybridizes to a human minisatellite, reveals complex polymorphic patterns in members of the Accipitridae, a family of 217 species of birds of prey, which includes the kites, hawks and eagles. The total absence of hybridization to males implies that the sequence is located on the W chromosome, and stable inheritance from mother to daughter suggests that the patterns evolve as haploid matrilines. This has allowed not only the development of a simple and rapid sexing technique but may also provide a means of monitoring matriarchal success and dispersion. As an example, a survey of 36 continental European red kite nests revealed 24 different haplotypes, whereas only 2 were found among 53 Welsh nests. The results show the effect of a dramatic bottleneck in Wales and may provide evidence of recent introgression from the continent.
Proceedings of The Royal Society of London. Series B, Biological Sciences (1934-1990), 1993
The genetic analysis of inbred populations has been facilitated by the development of Variable Nu... more The genetic analysis of inbred populations has been facilitated by the development of Variable Number Tandem Repeat (VNTR) probes. We describe here the first use of a synthetic, concatenated simple sequence probe to detect a single VNTR locus and its use in differentiating populations of the red kite, one of Europe's most threatened birds of prey. Numbering 11000-13000 pairs, this species is patchily distributed, comprising several populations, some of which have recently suffered major bottlenecks. By using the (CCAT)n probe we have examined variation within and among four of these. The levels of heterozygosity and allelic diversity reflect each population's history but also reveal substructuring within the indigenous British population in Wales. Here a group of peripheral territories, which are amongst the most successful in the population, exhibit significantly lower heterozygosity than the main population, and appear to receive little genetic input from it.
Crossover between the human sex chromosomes during male meiosis is restricted to the terminal pse... more Crossover between the human sex chromosomes during male meiosis is restricted to the terminal pseudoautosomal pairing regions. An obligatory exchange occurs in PAR1, an Xp/Yp pseudoautosomal region of 2.6 Mb, which creates a male-specific recombination 'hot domain' with a recombination rate that is about 20 times higher than the genome average. Low-resolution analysis of PAR1 suggests that crossovers are distributed fairly randomly. By contrast, linkage disequilibrium (LD) and sperm crossover analyses indicate that crossovers in autosomal regions tend to cluster into 'hot spots' of 1-2 kb that lie between islands of disequilibrium of tens to hundreds of kilobases. To determine whether at high resolution this autosomal pattern also applies to PAR1, we have examined linkage disequilibrium over an interval of 43 kb around the gene SHOX. Here we show that in northern European populations, disequilibrium decays rapidly with physical distance, which is consistent with this interval of PAR1 being recombinationally active in male meiosis. Analysis of a subregion of 9.9 kb in sperm shows, however, that crossovers are not distributed randomly, but instead cluster into an intense recombination hot spot that is very similar in morphology to autosomal hot spots. Thus, PAR1 crossover activity may be influenced by male-specific hot spots that are highly suitable for characterization by sperm DNA analysis.
Proceedings of The Royal Society of London. Series B, Biological Sciences (1934-1990), 1993
A red kite (Milvus milvus) clone, which cross-hybridizes to a human minisatellite, reveals comple... more A red kite (Milvus milvus) clone, which cross-hybridizes to a human minisatellite, reveals complex polymorphic patterns in members of the Accipitridae, a family of 217 species of birds of prey, which includes the kites, hawks and eagles. The total absence of hybridization to males implies that the sequence is located on the W chromosome, and stable inheritance from mother to daughter suggests that the patterns evolve as haploid matrilines. This has allowed not only the development of a simple and rapid sexing technique but may also provide a means of monitoring matriarchal success and dispersion. As an example, a survey of 36 continental European red kite nests revealed 24 different haplotypes, whereas only 2 were found among 53 Welsh nests. The results show the effect of a dramatic bottleneck in Wales and may provide evidence of recent introgression from the continent.
Uploads
Papers by Celia May