MBB 141 Questions 18-

18. The investigators in Question 17 were successful in purifying a BAC-DNA clone containing the gene for the mouse prion protein. They narrow down which region of the BAC DNA contains the prion-protein gene, they purified the BAC DNA, digested it with the restriction enzyme NotI, and separated the products of the enzymatic digestion by size using gel electrophoresis. Then, they purified each of the relatively large NotI DNA fragments from the gel, digested each individually with the restriction enzyme BamHI, and separated the products of each enzymatic digestion by size using gel electrophoresis. Finally, they transferred the size-separated DNA fragments from the agarose gel onto a membrane filter using the Southern blot technique, and allowed the DNA fragments on the filter to hybridize with a labeled cDNA probe. The figure above shows the results that were obtained: The pattern of DNA bands seen after the BAC DNA fragment is digested with NotI is shown in panel A; the pattern of DNA bands seen after each NotI fragment is digested with BamHI is shown in panel B; and the pattern of hybridizing DNA fragments visible after probing the Southern blot is shown in panel C.