Heritable fragile sites on human chromosomes II. Distribution, phenotypic effects, and cytogenetics

Individuals and families have been documented in which there are a number of fragile sites on chromosomes. These include sites at 2q11, 10q23, 11q13, 16p124, 16q22, 20p11, and Xq27 or 28. Fragile sites reported in the literature are compiled. The cytogenetics of the sites is discussed. The phenotypic effects of the sites are considered, and it is speculated that homozygosity of the autosomal sites might be deleterious as is hemizygosity of the site on Xq. These sites are used in the previous report which documents the effect of tissue medium components on their expression.