The fragile site (17)(p12): induction by AT-specific DNA-ligands and population cytogenetics

The rare fragile site at 17p12 can be induced in lymphocyte cultures with the AT-specific DNA-ligands distamycin A, DAPI, Hoescht 33258 and berenil. The optimum culture conditions for the experimental induction of fra(17)(p12) were studied. There are indications that fra(17)(p12) is a late-replicating chromosome region in which AT-rich DNA is located. The fragile site also occurs spontaneously in cell cultures of most fra(17)(p12) carriers. A population screening of 250 unselected individuals showed that the frequency of carriers heterozygous for fra(17)(p12) is 2%. The results are compatible with a population being in Hardy-Weinberg equilibrium with respect to fra(17)(p12) and its non-fragile allelomorph. Neither the heterozygous nor the homozygous condition of fra(17)(p12) have any deleterious effects.