Micronucleus formation in lymphocytes of patients with fraXq27 syndrome.

Human chromosome carry different fragile sites, but the most interesting one is the fragile X chromosome, especially in relation to mental retardation. In this report we present micronucleus formation in 5 individuals with the fragile X syndrome and 11 control subjects whose lymphocytes were cultured under 1) hydroxyurea treatment condition suitable for the increasing expression of the fraXq27, 2) control conditions. It has been found that hydroxyurea (HU) added to the final concentration 1.3 X 10(-5)M increases the frequency of the fraXq and micronucleus formation in comparison with culture without HU. The same concentration of HU has induced neither "nonspecific" "spontaneous" chromosomal breakage nor micronucleus formation in the control subjects.