A plasmid vector and chromosomal DNA are treated separately with the same restriction enzyme. The digested plasmid and chromosomal DNA were incubated together with DNA ligase and transformed into bacteria. Plasmids isolated from some of the colonies do not contain inserted chromosomal DNA. Which of the following could explain this observation?
A. The chromosomal DNA was very short and did not have any restriction sites for the enzyme used.
B. The two sticky ends of the plasmid could hybridize back together, recircularizing.
C. The two sticky ends of the plasmid could hybridize with two ends of another type of plasmid.
D. The two sticky ends of the vector would remain free or unhybridized.
E. The two sticky ends of the plasmid could hybridize to both sticky ends of the chromosomal DNA fragments.
Answer: B
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