Moderately repeated DNA sequences specific for the short arm of the human Y chromosome are present in XX males and reduced in copy number in an XY female.

Four DNA sequences specific for the Y chromosome were isolated from a recombinant phage library constructed from flow sorted human Y chromosomes. Two of these sequences were moderately repeated and assigned to the short arm of the Y chromosome by in situ hybridization. Both sequences were detected in five out of six [corrected] 46,XX males and were reduced in copy number in one out of two 46,XY gonadal dysgenesis patients tested. The findings suggest close proximity of these Y-specific moderately repeated DNA sequences to a testis determining locus.