Prader–Willi Syndrome and Angelman Syndrome in Cousins from a Family with a Translocation between Chromosomes 6 and 15

PRADER—WILLI syndrome represents the most common form of genetic obesity and is associated with mental retardation, short stature, sexual infantilism, and hypotonia1 2 3 4 5 6 (Table 1). In about 60 percent of affected persons a microscopically visible interstitial deletion in chromosome 15 (band ql2) is observed,2 , 3 , 7 8 9 10 and in up to 75 percent deletions can be found at the molecular level.11 122 13 14 DNA studies with polymorphic markers have indicated that in Prader-Willi syndrome the aberrant chromosome 15 is always of paternal origin,11 , 12 suggesting that the two parental chromosomes are differently imprinte1515 and that the presence of a gene or genes on the paternally . . .