Heritable fragile sites on human chromosomes. XII. Population cytogenetics.

Chromosome studies to detect the folate sensitive fragile sites have been carried out on 2439 randomly selected neonates. Four autosomal fragile sites were detected in this group. Similar studies were carried out on referred patients, special school students and sheltered workshop employees. The incidence of fragile X in these groups was 6/1936, 13/502 and 0/128 respectively. Autosomal folate sensitive fragile sites were seen in 14/1936, 5/502 and 2/128 individuals respectively.