Tease, C., Hartshorne, G. M. and Hultén, M. A.. (2002) Patterns of meiotic recombination in human fetal oocytes. American Journal of Human Genetics, Vol.70 (No.6). pp. 1469-1479. ISSN 0002-9297

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Abstract

Abnormal patterns of meiotic recombination (i.e., crossing-over) are believed to increase the risk of chromosome nondisjunction in human oocytes. To date, information on recombination has been obtained using indirect, genetic methods. Here we use an immunocytological approach, based on detection of foci of a DNA mismatch-repair protein, MLH1, on synaptonemal complexes at prophase I of meiosis, to provide the first direct estimate of the frequency of meiotic recombination in human oocytes. At pachytene, the stage of maximum homologous chromosome pairing, we found a mean of 70.3 foci (i.e., crossovers) per oocyte, with considerable intercell variability (range 48-102 foci). This mean equates to a genetic-map length of 3,515 cM. The numbers and positions of foci were determined for chromosomes 21, 18, 13, and X. These chromosomes yielded means of 1.23 foci (61.5 cM), 2.36 foci (118 cM), 2.5 foci (125 cM), and 3.22 foci (161 cM), respectively. The foci were almost invariably located interstitially and were only occasionally located close to chromosome ends. These data confirm the large difference, in recombination frequency, between human oocytes and spermatocytes and demonstrate a clear intersex variation in distribution of crossovers. In a few cells, chromosomes 21 and 18 did not have any foci (i.e., were presumptively noncrossover); however, configurations that lacked foci were not observed for chromosomes 13 and X. For the latter two chromosome pairs, the only instances of absence of foci were observed in abnormal cells that showed chromosome-pairing errors affecting these chromosomes. We speculate that these abnormal fetal oocytes may be the source of the nonrecombinant chromosomes 13 and X suggested, by genetic studies, to be associated with maternally derived chromosome nondisjunction.

Item Type:	Journal Article
Subjects:	Q Science > QH Natural history > QH426 Genetics R Medicine > RG Gynecology and obstetrics
Divisions:	Faculty of Science > Life Sciences (2010- ) > Biological Sciences ( -2010)
Library of Congress Subject Headings (LCSH):	Meiosis, Genetic recombination -- Research, Ovum, Oogenesis, Crossing over (Genetics), Fluorescence in situ hybridization
Journal or Publication Title:	American Journal of Human Genetics
Publisher:	Elsevier
ISSN:	0002-9297
Official Date:	June 2002
Dates:	Date Event June 2002 Published
Volume:	Vol.70
Number:	No.6
Number of Pages:	11
Page Range:	pp. 1469-1479
Identification Number:	10.1086/340734
Status:	Peer Reviewed
Publication Status:	Published
Funder:	WellBeing (Organization) (WBW), Wellcome Trust (London, England)
Grant number:	H1/98 (WBW), 061202/ZOOZ (WT)
URI:	http://wrap.warwick.ac.uk/id/eprint/10973

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