This book comprises the written proceedings of a symposium on Down's syndrome that was held in Boston in 1978. The editors have drawn on a group of well-recognized leaders in Down's syndrome research to submit 19 contributions to this book, which is divided into five sections.
The first section discusses the epidemiology of Down's syndrome and accounts for over one third of the written pages. Ernest Hook presents a comprehensive analysis of the frequency of Down's syndrome in human populations and factors that may affect its frequency. The next three articles present observations that, when taken in aggregate, challenge the traditional assumption that the extra 21 chromosome arises only from meiotic nondisjunction in the mother. How does one reconcile the observations that 25% of persons with Down's syndrome derive the extra 21 chromosome from the father and that the majority of trisomy 21 conceptuses do not come to term but