Molecular Biology/Genetics USMLE Step 1 Practice Question
A 2-year-old obese female has been diagnosed with Prader-Willi syndrome. To confirm the diagnosis, a DNA methylation assay is performed. A sample of her DNA is first cut with EcoRI, releasing a 12-kb fragment, shown below, which is detected by the probe for the involved region on chromosome 15. This fragment is then treated with a second restriction endonuclease that cuts within a CGCGCG sequence located at the position indicated by the arrow. If the CGCGCG sequence is methylated, the restriction endonuclease will not cut it. Assuming that the results confirm the diagnosis of Prader-Willi, which pattern below represents the patient's DNA?
Answer choices
- AE
- BD
- CC
- DB
- EACorrect answer
- FF
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