Restriction enzyme Hpall cuts the sequence CCGG, Hpal s sensitive to CpG methyla

Question

Restriction enzyme Hpall cuts the sequence CCGG, Hpal s sensitive to CpG methylation: it cannot cut if the second C is methylated. The following map depicts the promoter region of the maternally imprinted gene: the two middle Hpall sites are methylated when inherited from mother. You digest human blood DNA with Hpall and probe with the 400 base pair probe (dashed line). What bands would you expect to a. 400 bp b. 800 bp c. 400 bp and 500 bp d. 400 bp and 800 bp e. Depends on the sex of the individual tested If you performed the same digestion and Southern hybridization with sperm DNA, what bands would you expect to see? a. 400 bp b. 500 bp c. 800 bp d. 400 bp and 500 bp e. 400 bp and 800 bp p53 is a tumor suppressor gene required to G1-S checkpoint. Participating in the Undergraduate Research Program, you identified a new transcription factor, which is absolutely required for expression of p53. You named this new transcription factor RPE (Required for P53 Expression). Based on your knowledge of carcinogenesis, you hypothesize that: a. RPE is a proto-oncogene b. RPE is a tumor suppressor gene c. RPE is neither tumor suppressor gene nor a proto-oncogene d. RPE could be either a tumor suppressor gene or a proto-oncogene

Explanation / Answer

21: b: 800 bp

Explanation: Hpall is a type II DNA restriction enzyme which carry out the endonucleolytic cleavage of DNA. As the map shows the promoter region of the maternally imprinted gene, and two middle Hpall sites are methylated. Therefore Hpall will not cut this DNA segment from middle sites after digestion of human blood DNA with Hpall and 400 bp probe, and the band of 800 bp will be seen.

22: c: 800 bp

Explanation: As the digestion process is same, therefore 800 bp band will appear. Southern hybridization with sperm DNA will only minimize the son specific attachment of probe to the nylon membrane by blocking the membrane surface.

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