1, 9, and 16 C-band heteromorphisms in parents of Down's syndrome patients: Distribution and etiological significance

Summary The C-band areas of chromosomes 1, 9, and 16 were studied in 50 Japanese individuals, parents of Down's syndrome patients. In order to measure these areas, a modular system for semiautomatic quantitative evaluation of images (VIP-11, Olympus) was used. Each area was distributed according to a system of classfication proposed by Patil and Lubs (1977). The distribution of the C-band areas for each chromosome appeared to be significantly different from the distribution of these areas in a normal population chosen at random. The role that large constitutive heterochromatin variants may have in the occurrence of nondisjunction is considered.