Turner's syndrome and 46,X,i(Yq) karyotype.

A patient with features of Turner's syndrome is reported. In her karyotype there were 46 chromosomes including 15 chromosomes in the C group and one metacentric marker the size of a No. 16. This marker was identified through its fluorescence pattern as being an isochromosome for the long arm of the Y. This observation strongly suggests that the male determining factors are situated on the short arm of the Y chromosome.