Classification of Y chromosome polymorphisms by DNA content and C-banding.

A system has been developed using a microscope photometer to measure the DNA content of individual chromosomes. After correcting for the systematic and statistical errors the measured values are highly reproducible. Data are presented of measurements of human Y chromosomes from a cytogenetically normal population. When compared with the C-banding pattern from the same specimens the DNA content is found to change in discrete steps of 1.36 x 10(-14)g or 13.26 x 10(6) bp for each of the Y chromosome polymorphic types.