Highly homologous loci on the X and Y chromosomes are hot-spots for ectopic recombinations leading to XX maleness.
In 80% of XX males, maleness is due to the presence of Y-specific DNA including the SRY gene and results from an abnormal terminal X-Y interchange during paternal meiosis. Here we address the molecular basis of this ectopic recombination through the analysis of the X-Y junction in two class 3 XX males. We show that each of the rearrangements has involved X-Y highly homologous loci on the sex-specific part of these chromosomes (98.7% and 96% sequence identity over 1.2 and 1.1 kb respectively). Moreover in five out of six other XX males, the X-Y junctions are located in the same rearranged restriction fragment as in either of these patients. These fragments thus define two hot-spots of ectopic recombination which together could account for about one third of XX males. Evolution of these loci in primates is discussed.
Weil
D
D
Unité de Génétique Moléculaire Humaine, CNRS URA 1445, Institut Pasteur, Paris, France.
Wang
I
I
Dietrich
A
A
Poustka
A
A
Weissenbach
J
J
Petit
C
C
D000818:Animals; D001483:Base Sequence; D005075:Biological Evolution; D003434:Crossing Over, Genetic; D004276:DNA, Satellite / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics*; D006801:Humans; D008297:Male; D008969:Molecular Sequence Data; D009687:Nuclear Proteins; D011323:Primates / Q000235:genetics; D012091:Repetitive Sequences, Nucleic Acid; D016415:Sequence Alignment; D012689:Sequence Homology, Nucleic Acid; D012729:Sex Chromosome Aberrations / Q000235:genetics*; D012732:Sex Determination Analysis; D051876:Sex-Determining Region Y Protein; D014157:Transcription Factors; D014960:X Chromosome / Q000648:ultrastructure; D014998:Y Chromosome / Q000648:ultrastructure
D004276:DNA, Satellite; D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; C497745:SRY protein, human; D051876:Sex-Determining Region Y Protein; D014157:Transcription Factors