Two diagrams below show the special connections shared by the common deletion on 15th chromosome which, in turn, become Prader-Willi Syndrome, Angelman's Syndrome, and Dup15q syndrome.

 

IPWSO - www.ipwso.org

Angelman Syndrome Foundation, Inc. - www.angelman.org

Dup15 Alliance - www.idic15.org/Chromosome-15-duplications.html