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Signs/symptoms

• hand-flapping
• jerky body movement
• a stiff-legged gait
• little or no speech
• attention deficits
• hyperactivity
• feeding and sleeping problems (especially in infancy)
• delays in motor development

Causes

Prader-Willi syndrome and Angelman syndrome are two rare chromosome disorders, with very different symptoms, but caused by the same area of DNA. They are important to genetic research because they are caused by imprinting.


Risk factors
Angelman syndrome is rare. In most cases, researchers don't know what causes the genetic changes that result in Angelman syndrome. Most people with Angelman syndrome don't have a family history of the disease. In a small percentage of cases, however, Angelman syndrome may be inherited from a parent, so a family history of the disease may increase a baby's risk of developing Angelman syndrome.

Diagnosis
The diagnosis of Angelman syndrome rests upon a combination of clinical features and molecular genetic testing and/or cytogenetic analysis. Consensus clinical diagnostic criteria for AS have been developed. Analysis of parent-specific DNA methylation imprints in the 15q11.2-q13 chromosome region detects approximately 78% of individuals with AS, including those with a deletion, uniparental disomy, or an imprinting defect; fewer than 1% of individuals have a cytogenetically visible chromosome rearrangement (i.e., translocation or inversion). UBE3A sequence analysis detects mutations in an additional ~11% of individuals. Accordingly, molecular genetic testing (methylation analysis and UBE3A sequence analysis) identifies alterations in about 90% of individuals. The remaining 10% of individuals with classic phenotypic features of AS have a presently unidentified genetic mechanism and thus are not amenable to diagnostic testing.
• A history of delayed motor...