RECURRENT DUPLICATION AND DELETION POLYMORPHISMS ON THE LONG ARM OF THE Y-CHROMOSOME IN NORMAL MALES

Deletion of the 50f2/C (DYS7C) locus in interval 6 of Yq has previousl y been reported as a polymorphism in three males. We describe a survey of worldwide populations for further instances of this deletion. Of 8 59 males tested, 55 (similar to 6%) show absence of the 50f2/C locus; duplication of the locus was also detected in eight out of 595 males ( similar to 1.4%). Populations having the deletion are confined to Asia , Australasia, and southern and northern Europe; of those of reasonabl e sample size, Finns had the highest deletion frequency (55%; n = 21). The deletions vary in size and the larger ones remove some of the RBM (RNA Binding Motif) genes, but none of the deletion males lack DAZ (D eleted in AZoospermia), a candidate gene for the azoospermia factor. O n a tree of Y haplotypes, 28 deletion and eight duplication chromosome s fall into six and four haplotypic groups respectively, each of which is likely to represent an independent deletion or duplication event. Microsatellite and other haplotyping data suggest the existence of at least two further classes of deletion. Thus duplications and deletions in this region of Yq have occurred many times in human evolution, but remain useful markers for paternal lineages.