title: Sex chromosome synapsis and recombination in male guppies.
abstract: Guppy X and Y chromosomes represent an early stage in sex chromosome divergence. Synapsis and recombination between X and Y chromosomes attract special attention because recombination suppression promotes their differentiation, but previous studies have given contradictory results. Linkage analysis indicated that recombination between X and Y was extremely rare (<10%) and occurred in the medial part of the Y chromosome, while cytological analysis demonstrated regular association between the distal ends of the X and Y at diakinesis. In this study, we examine pairing and recombination between X and Y chromosomes using immunolocalization of MLH1 to mark recombination nodules, and genomic in situ hybridization with a male DNA probe to identify the Y-specific heterochromatic region. Pairing between X and Y is initiated distally. Single crossovers were detected in 87% of XY synaptonemal complexes, most often in the distal region and less frequently in a median position indicating that end-to-end associations between X and Y are chiasmatic. Thus, we suggest that the very low frequency of recombination detected by linkage analysis in a previous study resulted from a lack of informative markers in distal regions.
authors.affiliation: 1 Institute of Cytology and Genetics, The Siberian Branch of the Russian Academy of Sciences , Novosibirsk, Russia .
authors.forename: Artem P
authors.initials: AP
authors.lastname: Lisachov
authors.forename: Kira S
authors.initials: KS
authors.lastname: Zadesenets
authors.forename: Nikolay B
authors.initials: NB
authors.lastname: Rubtsov
authors.forename: Pavel M
authors.initials: PM
authors.lastname: Borodin
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism; D000818:Animals; D023902:Chromosome Pairing; D005786:Gene Expression Regulation; D005819:Genetic Markers; D059785:Karyotype; D008297:Male; D000070957:MutL Protein Homolog 1; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D011036:Poecilia / Q000235:genetics*; D011995:Recombination, Genetic / Q000235:genetics*; D012730:Sex Chromosomes / Q000235:genetics*; D029961:Zebrafish Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D005819:Genetic Markers; C530170:Mlh1 protein, zebrafish; D009687:Nuclear Proteins; D029961:Zebrafish Proteins; D000070957:MutL Protein Homolog 1