pBR322 DNA (4.32 kb) was cleaved with Hindlll nuclease and lig-ated to a Hindlll digest of...

pBR322 DNA (4.32 kb) was cleaved with Hindlll nuclease and lig-ated to a Hindlll digest of human mitochondrial DNA. One recombinant plasmid DNA was analyzed by gel electrophoresis of restriction cleavage fragments, with the following results: lane A = EcoRI-treated recombinant, lane B = HindIII-treated vector, and lane C = HindIII-treated recombinant.

(a) Why was the recombinant plasmid treated with EcoRI for determination of its size?

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 (b) How might you explain the discrepancy between the size of the recombinant molecule and the sum of the sizes of the Hindlll cleavage fragments?

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 (c) Draw a diagram of the recombinant showing the locations of the Hindlll cleavage sites.