Published online by Cambridge University Press: 14 April 2009
The frequencies of non-disjunction at first and second meiotic division, in both male and female of Drosophila melanogaster, are estimated. Numbers of exceptional individuals scored in several broods of increasing parental age are also presented. These results fail to show any evidence of an age-effect. Work claiming to demonstrate the existence of an age effect in Drosophila is reinvestigated. The importance of these results and their relevance to human studies are discussed.