Tooth size in 47, XYY males: evidence for a direct effect of the Y chromosome on growth*

Mean values of deciduous and permanent tooth dimensions were compared between 47, XYY males and control subjects to clarify the role of the Y chromosome in dental development. Tooth size was generally larger in the 47, XYY sample, although the increase in size was not uniform throughout the dentition. The Y chromosome appears to have a direct effect on tooth size which may be due to a specific gene (or genes) or may be related to a more non‐specific effect of heterochromatin on cellular activity.