The genetic relationship between PWS and AS is remarkable. They are both
generally associated with a cytogentic deletion of on the long arm of
chromosome 15 (15q11q13), or uniparental disomy of chromosome 15.
However, PWS patients have the deletion on the chromosome of paternal
origin or maternal disomy; AS patients have the deletion on the chromosome
of maternal origin or parental disomy.
Apparently parental imprinting is responsible: failure to express from the
paternal copy (for whatever reason) results in PWS, and failure to express
from the maternal copy results in AS.
I gleened all of this from Marc E. Lalande's work described in the 1994
Howard Hughes Medical Institute publication _Research_In_Progress_. Hope
it helps.
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Dan Weinreich email: dmw at mcz.harvard.edu
Harvard University usmail: 26 Oxford Street
Museum of Comparative Zoology Cambridge, MA 02138
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