The origin of the extra Y chromosome in males with a 47,XYY karyotype.
The presence of an extra Y chromosome in males is a relatively common occurrence, the 47,XYY karyotype being found in approximately 1 in 1000 male births. The error of disjunction must occur either during paternal meiosis II or as a post-zygotic mitotic error, both of which are rare events for other chromosomes. It is therefore of interest to determine when errors of Y chromosome disjunction occur. It is possible to distinguish between the different mechanisms of non-disjunction by analysing DNA polymorphisms at the distal tip of the Xp/Yp pseudoautosomal region in 47,XYY males, their parents and in some cases paternal grandparents. A cohort of 28 non-mosaic 47,XYY males was analysed. The results show that there are at least two mechanisms causing non-disjunction of the Y chromosome. In 16 of the 19 cases from which parents were available, the extra Y was generated by non-disjunction at meiosis II after a normal chiasmate meiosis I. Three cases were due to either a post-zygotic mitotic error or non-disjunction at meiosis II after a nullichiasmate meiosis I. Of the nine cases with no parental DNA available, at least four were due to meiosis II non-disjunction following a normal chiasmate meiosis I.
Robinson
D O
DO
Wessex Regional Genetics Laboratory, Salisbury District Hospital, Salisbury, Wiltshire SP2 8BJ, UK. drobinso@hgmp.mrc.ac.uk
Jacobs
P A
PA
D001483:Base Sequence; D017931:DNA Primers; D005260:Female; D006801:Humans; D007621:Karyotyping; D008297:Male; D010375:Pedigree; D012729:Sex Chromosome Aberrations; D014314:Trisomy; D014998:Y Chromosome
D017931:DNA Primers