Prader-Willi Syndrome is also a genetic disorder that's caused by a deletion of a gene or something on chromosome 15. Sometimes the daddy's chromosome 15 doesn't get passed to the baby, which is not good, or the baby gets two of the mommy's number 15 chromosome, and since the mommy's number 15 is not active, the baby has no chromosome 15. Sometimes translocation occurs on the chromosome, so some of the chromosome 15 goes and attaches to another chromosome. And sometimes, very rarely though, the chromosome is imprinted incorrectly and the mommy's copy and daddy's copy act differently. All of this sounds pretty smart, but for once i sort of understand what I'm saying. It would be so much better though if i could actually find someone who could give me information that has actually seen or dealt with Prader-Willi Syndrome..