On the peripheral location of the Y chromosome

The location of the Y chromosome in metaphase spreads is studied in groups of (a) 96 normal males, (b) 17 Down's syndrome patients, and (c) 51 patients with Klinefelter's syndrome. The position of the Y is scored as either peripheral or nonperipheral using several of the traditional definitions found in the literature. It is shown that contradictory results may be obtained depending on the particular definition employed and that none of the available definitions capture the essence of the meaning of 'peripheral'. Therefore a new, standardized definition is introduced-one that applies to both circular and noncircular spreads. Using this new definition, we find definite intergroup variability. The Y is peripheral in normal males, but not in either the Down's or Klinefelter's samples.