Tease, C. and Hultén, Maj A.. (2004) Inter-sex variation in synaptonemal complex lengths largely determine the different recombination rates in male and female germ cells. Cytogenetic and Genome Research, Vol.107 (No.3-4). pp. 208-215. ISSN 1424-8581

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Abstract

Meiotic chromosomes in human oocytes are packaged differently than in spermatocytes at the pachytene stage of meiosis I, when crossing-over takes place. Thus the meiosis-specific pairing structure, the synaptonemal complex (SC), is considerably longer in oocytes in comparison to spermatocytes. The aim of the present study was to examine the influence of this length factor on meiotic recombination in male and female human germ cells. The positions of crossovers were identified by the DNA mismatch repair protein MLH1. Spermatocytes have approximately 50 crossovers per cell in comparison to more than 70 in oocytes. Analyses of inter-crossover distances ( and presumptively crossover interference) along SCs suggested that while there might be inter-individual variation, there was no consistent difference between sexes. Thus the higher rate of recombination in human oocytes is not a consequence of more closely spaced crossovers along the SCs. The rate of recombination per unit length of SC is higher in spermatocytes than oocytes. However, when the so-called obligate chiasma is excluded from the analysis, then the rates of recombination per unit length of SC are essentially identical in the two sexes. Our analyses indicate that the inter-sex difference in recombination is largely a consequence of the difference in meiotic chromosome architecture in the two sexes. We propose that SC length per se, and therefore the size of the physical platform for crossing-over ( and not the DNA content) is the principal factor determining the difference in rate of recombination in male and female germ cells. A preliminary investigation of SC loop size by fluorescence in situ hybridization ( FISH) indicated loops may be shorter in oocytes than in spermatocytes. Copyright (C) 2004 S. Karger AG, Basel.

Item Type:	Journal Article
Subjects:	Q Science > QH Natural history > QH426 Genetics Q Science > QP Physiology
Divisions:	Faculty of Medicine > Warwick Medical School
Library of Congress Subject Headings (LCSH):	Germ cells, Meiosis, Intersexuality, Fluorescence in situ hybridization, Crossing over (Genetics)
Journal or Publication Title:	Cytogenetic and Genome Research
Publisher:	Karger
ISSN:	1424-8581
Date:	2004
Volume:	Vol.107
Number:	No.3-4
Number of Pages:	8
Page Range:	pp. 208-215
Identification Number:	10.1159/000080599
Status:	Peer Reviewed
Publication Status:	Published
Access rights to Published version:	Restricted or Subscription Access
Funder:	Wellcome Trust (London, England)
Grant number:	061202/ZOOZ (WT)
URI:	http://wrap.warwick.ac.uk/id/eprint/7809

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