Which of the following restriction enzyme/endonuclease is most widely used in genetic engineering?
A
RE Type I
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B
RE Type II
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C
RE Type III
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D
Both A & C
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Solution
The correct option is B RE Type II
There are three classes of restriction enzymes, labeled type I, II, and III.
Type I restriction systems have a single enzyme that modifies (methylation) the DNA strand at a specific recognition site but restriction activities occur randomly and away from the recognition site.
Type III restriction systems have separate enzymes for restriction activity and methylation and cleave outside the restriction site.
Thus, both Type I and III are not used in genetic engineering.
While Type II restriction enzymes are highly useful in recombinant DNA techniques because they have a separate specific enzyme for restriction which cleaves at the specific sequence site.
One enzyme recognizes and cuts the DNA, the other enzyme recognizes and methylates the DNA.