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Unformatted text preview: Imprinting ©J.L.Marsh 137B November 29, 2004 page 1 IMPRINTING - THE STORY OF PRADER-WILLI & ANGELMAN SYNDROMES Phenotype(s) = rare = 1/25,000 or ~1,600 in USA Prader Willi patients = hyperphagia leading to obesity no evidence of puberty- hypogonadism small hands & feet mental retardation Angelman syndrome = happy puppet syndrome Laugh uncontrollably hypopigmentation both ocular & general mental retardation First described in 1965 & 222 children w/syndrome reported by 1991 Resources: http://www.ahsc.arizona.edu/msrgsn/gd/gdvol10c.htm genetics newsletter http://asclepius.com/angel/asfinfo.html = facts about angleman Genetics Prader-Willi & Angelman map near each other on chr 15 Expression of the disease shows Parent of Origin Bias. 1] e.g. Inheritance of deletions shows parental source bias in terms of disease 70-80% of PW cases are inheritance of spontaneous deletion 15q & imprinting What is unusal here? Does not obey Mendel. Why? Lack of reciprocity Δ /+ +/+ all normal Δ /+ +/+ Δ /+ +/+ Angelman syndrome Δ /+ +/+ Δ /+ +/+ all normal...
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- DNA, uniparental disomy, Δ/+ +/+