Aneuploidy is the second most important category of chromosome mutations relating to abnormal chromosome number. It generally arises by nondisjunction at either the first or second meiotic division. However, the existence of two chromosomal abnormalities involving both autosomal and sex chromosomes in the same individual is relatively a rare phenomenon. The underlying mechanism involved in the formation of double aneuploidy is not well understood. Parental origin is studied only in a small number of cases and both nondisjunctions occurring in a single parent is an extremely rare event. This chapter reviews the characteristics of double aneuploidies in Down syndrome have been discussed in the light of the published reports.
Part of the book: Health Problems in Down Syndrome