title: Variation in meiotic recombination frequencies among human males.
abstract: Meiotic recombination is essential for the segregation of homologous chromosomes and the formation of normal haploid gametes. Little is known about patterns of meiotic recombination in human germ cells or the mechanisms that control these patterns. Here, newly developed immunofluorescence techniques, based on the detection of MLH1 (a DNA mismatch repair protein) foci on synaptonemal complexes (SCs) at prophase I of meiosis, were used to examine recombination in human spermatocytes. The mean number of MLH1 foci per cell in all donors was 48.0 with range from 21 to 65. Remarkable variation in the recombination frequency was noted among 11 normal individuals: the mean frequencies of chromosomal recombination foci ranged from a low of 42.5 to a high of 55.0 exchanges. Donor age did not contribute to this variation. There was no correlation between this variation and the frequency of gaps (discontinuities) or splits (unpaired chromosome regions) in the SCs. The mean percentage of cells with gaps was 35% (range: 20% to 58%) and with splits was 7% (range: 0% to 37%). Bivalents without a recombination focus were rare, with a frequency of only 0.3%. Thus, achiasmate chromosomes appear to be rare in human male meiosis.
authors.affiliation: Department of Medical Genetics, University of Calgary, Calgary, T2N 4N1, Canada.
authors.forename: Fei
authors.initials: F
authors.lastname: Sun
authors.forename: Kiril
authors.initials: K
authors.lastname: Trpkov
authors.forename: Alfred
authors.initials: A
authors.lastname: Rademaker
authors.forename: Evelyn
authors.initials: E
authors.lastname: Ko
authors.forename: Renée H
authors.initials: RH
authors.lastname: Martin
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D002352:Carrier Proteins; D006801:Humans; D008297:Male; D008540:Meiosis; D049469:Meiotic Prophase I; D008875:Middle Aged; D000070957:MutL Protein Homolog 1; D009363:Neoplasm Proteins / Q000235:genetics*; D009687:Nuclear Proteins; D011995:Recombination, Genetic; D013090:Spermatocytes / Q000502:physiology*; D013573:Synaptonemal Complex / Q000502:physiology
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; C501486:MLH1 protein, human; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D000070957:MutL Protein Homolog 1