Sister chromatid exchange in families with Angelman or Prader-Willi syndrome.

Using estimation of numbers of sister chromatid exchanges arising in 15q11q13 as a measure, comparisons of the stability of the Prader-Willi syndrome critical region have been made. The groups studied included probands with Prader-Willi or Angelman syndromes either with or without a cytogenetically visible deletion in 15q11q13, their parents, specifically those parents who had passed on the homologue which had become deleted, and a control group. No significant differences were found between any of the four groups, indicating that there was no increase in the instability of the PWSCR region as measured by sister chromatid exchange.