Crossing over analysis at pachytene in man

Abstract

The distribution of anti-MLH1 (MutL homologue 1) antibody labelling was studied in human prophase meiocytes. A labelling pattern consisting of distinct foci, always associated with the synaptonemal complex (SC) and never in closely juxtaposed pairs, was observed. Comparison of the number and general positions of autosomal foci with previous studies of the number and positions of autosomal chiasmata indicates that the anti-MLH1 antibody marks sites of crossing over in human pachytene spermatocytes. A mean number of 50.9 autosomal foci was observed from 46 human pachytene spermatocytes corresponding to a genetic length of 2545 cM. Division of these spermatocytes into sub-stages revealed that the number of foci remains stable throughout pachytene. A focus was found on the XY bivalent in 56.5% of the nuclei. The presence or absence of foci from the XY bivalent could not be correlated to pachytene sub-stage.

Analysis of Arabidopsis genome-wide variations before and after meiosis and meiotic recombination by resequencing Landsberg erecta and all four products of a single meiosis

“…Recent studies indicated that between individuals of the same species for human and others, the genetic distance (CO number) is positively correlated with the length of the synaptonemal complex (SC) but not the length of DNA (Lynn et al 2002;Kleckner et al 2003). However, this correlation does not seem to hold between species; for example, human, Arabidopsis, and the budding yeast have SC lengths per chromosomes of approximate 10-25, 2-3, and 1-2 microns, yet the CO numbers per chromosomes are 1-3, 1-3, and 2-11, respectively (Dresser and Giroux 1988;Barlow and Hulten 1998;Wijeratne et al 2006). Strikingly, the ratios of genome size to SC length are very similar between human (;10-12 Mb/micron) and Arabidopsis (;12 Mb/micron), but much smaller in the budding yeast (;0.5 Mb/micron).…”

“…Possible relationship between frequency of CO, genome size, and length of synaptonemal complex Human and mouse, as well as other animals and plants, have very different genome sizes, yet all have one to three COs per homolog pair (Baker et al 1995;Barlow and Hulten 1998), similar to Arabidopsis, but unlike the two to 11 COs per chromosome in the budding yeast (Mancera et al 2008;Qi et al 2009) (Supplemental Table 16). Recent studies indicated that between individuals of the same species for human and others, the genetic distance (CO number) is positively correlated with the length of the synaptonemal complex (SC) but not the length of DNA (Lynn et al 2002;Kleckner et al 2003).…”

Meiotic recombination and male infertility: from basic science to clinical reality?

“…35 The average number of recombinatorial events per cell in control males has been shown to be approximately 50 through cytogenetic studies and immunofluorescence data. 36,[38][39][40][41][42] There is a significant degree of variability between controls (13-25%) and between cells from the same individual (range: 42.5-55.3 recombination foci per cell). [39][40][41][42] The majority of published studies provide evidence of a significant reduction in recombination events per cell in NOA individuals compared to controls (40-42 versus 46-49).…”

Errors in Chromosome Segregation During Oogenesis and Early Embryogenesis

“…First, crossover frequency and distribution along the lengths of individual chromosomes can be identified in fetal oocytes by analysis of the meiotic chromosome pairing structure, the Synaptonemal Complex (SC) using immunofluorescence against recombination proteins [2][3][4][5][6] . Second, there is the potential to identify crossover frequency and distribution in the form of chiasmata at the MI stage ( 7 ).…”