Restudy of the original marker X family.

Restudy of the original marker-X family confirmed recent observations that this XLMR disorder is associated with large testes and slightly abnormal ears. However, other aspects of the phenotype were variable and a distinct facies was not evident. Significant differences in marker-X frequency between two laboratories processing the same samples were observed. Possibly, the combination of more cells and a longer culture time in one laboratory led to a greater depletion of critical nutrients and a higher frequency of the marker-X, but additional studies are needed. No evidence was found of a diminishing frequency of the marker-X over a 15 year period.