Question

Restriction endonucleases are

• A. Synthesized by bacteria
• B. Present in cells for degradation of foreign DNA
• C. Used in genetic engineering
• D. All of the above

Answer 1

Answer: (D)

Restriction enzyme is a protein produced by bacteria that cleaves DNA at specific sites along the molecule. In the bacterial cell, restriction enzymes cleave foreign DNA, thus eliminating infecting organisms.

The goal of genetic engineering is changing the genetic makeup of an organism. To achieve this goal, scientists must have a way of rearranging genes to create new combinations of DNA. Restriction enzymes are one tool that can be used to accomplish this goal. A restriction enzyme or restriction endonuclease is an enzyme that cuts DNA at or near specific recognition nucleotide sequences known as restriction sites. To cut DNA, all restriction enzymes make two incisions, once through each sugar-phosphate backbone (i.e., each strand) of the DNA double helix.

Therefore, the correct answer is option D.