UBC Theses and Dissertations
Chromosome segregation and meiotic defects in carriers of chromosomal abnormalities Kirkpatrick, Gordon
Male carriers of chromosomal abnormalities (CA) are more frequent in the infertile population. These men have higher levels of sperm aneuploidy due to the aberrant segregation of the chromosomes involved in the abnormality. The presence of a CA may also influence the segregation of other chromosomes, in a process known as in interchromosomal effect (ICE). The behaviour of the CA during meiosis may account for the infertility observed in this population. We studied chromosome segregation, ICE and meiotic defects in a variety of CA. In carriers of CA, we determined the segregation patterns of chromosomes involved in the abnormality. With the exception of the carriers of mosaic aneuploidy, we found significantly increased frequencies of unbalanced chromosome complements. We observed ICE in six of twelve carriers, which were confined largely to the acrocentric chromosomes 13 and 21. We compared the frequency of chromosome imbalance in CA carriers with infertile, but karyotypically normal, and found higher levels of sperm aneuploidy than CA carriers or controls. We observed synapsis and recombination of homologous chromosomes in carriers of chromosomal abnormalities, as well infertile and fertile men. We observed reduced recombination in two of the carriers of CA and in three of the infertile men. Increased synaptic errors were observed in all carriers of CA and in four of the infertile men. We noted an increased proportion of cells lacking sex chromosome recombination in all of the CA carriers. We studied chromosome-specific recombination patterns on chromosomes 13, 18 and 21 and compared those results with levels of aneuploidy in the sperm but observed no relationship. We studied the recombination and sex chromosome association, of the involved chromosomes, in the three carriers of CA, and observed decreased recombination on the involved chromosomes and frequent association between the chromosome abnormality and the sex chromosomes. We report the use of a novel technique for the examination of meiotic cells derived from the ejaculate. We compared spermatocytes, derived from the ejaculate, with testicular derived spermatocytes and found no difference in the frequency of global or chromosome-specific recombination, synaptic errors or proportion of cells at various stages of prophase.
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