SPONTANEOUS AND INDUCED MINISATELLITE INSTABILITY

Minisatellites provide not only the basis for DNA fingerprinting and D NA profiling but also extremely informative systems for analysing proc esses of tandem repeat turnover in the human genome. Minisatellite ins tability appears to involve distinct mutation processes in somatic and germline cells; in the germline, mutation is frequently dominated by inter-allelic conversion-like events most likely occurring at meiosis and apparently regulated by cis-acting mutation initiator elements. At tempts to define these initiators in transgenic mice have so far been thwarted by what appears to be a major human/mouse barrier to the inte r-species transfer of repeat instability. Minisatellites not only show high frequency spontaneous mutation in the germline, but also appear to be very sensitive to mutation induction by ionizing radiation, both in experimentally irradiated mice and in human populations exposed fo llowing the Chernobyl disaster; the mechanisms of mutation induction b y radiation remain enigmatic.