Question

Restriction endonuclease

• A. synthesizes DNA
• B. Cuts the DNA molecule randomly
• C. Cuts the DNA molecule at specific sites
• D. Restricts the synthesis of DNA inside the nucleus

Answer 1

Answer: (C)

Cuts the DNA molecule at specific sites

A restriction enzyme is a protein that recognises a specific, short nucleotide sequence and cuts the DNA only at that specific site, which is known as restriction site or target sequence. A bacterium is immune to its own restriction enzymes, even if it has the target sequences ordinarily targeted by them. This is because the bacterial restriction sites are highly methylated, making them unrecognizable to the restriction enzyme. When a restriction enzyme cleaves a restriction site, the reaction creates highly reactive "sticky ends" on the broken DNA. This is useful to the biotechnologist .By cutting open vector DNA with the same restriction enzymes used to cleave the target DNA, complementary "sticky ends" are created. The fragment is "glued in" with DNA ligase, which creates the phosphodiester bonds necessary to complete the sugar phosphate backbone of the new recombinant DNA.
So, the correct option is option C.