IDENTIFICATION OF INTERNAL VARIATION IN THE PSEUDOAUTOSOMAL VNTR DXYS17, WITH NONRANDOM DISTRIBUTION OF THE ALLELES ON THE X-CHROMOSONE ANDTHE Y-CHROMOSOME

The PCR technique was used to analyze the DXYS17 locus in the pseudoau tosomal region of the X and the Y chromosomes. Analysis on an automate d DNA sequencer allowed for sensitive and highly accurate typing of 16 different alleles with a size between 480 and 1,100 bp. Two DXYS17 al leles migrated with the same size on agarose or denaturing polyacrylam ide gels but with different mobilities on nondenaturing polyacrylamide gels. Sequence analysis showed that, while an identical number of rep eats were present in both alleles, differences in the composition of t he units were observed. The origin of these differences was found in t he 28- and 33-bp units, which only had a specific repeat pattern at th e 5' and 3' ends of the region. The genotype distribution for DXYS17 i n a Caucasian population did not deviate from the values expected unde r Hardy-Weinberg equilibrium. However, the frequency of one allele and one genotype was significantly different between males and females. S egregation analysis showed that this difference was the result of a no nrandom distribution of certain alleles on the sex chromosomes in male s.