Which of the following statements are not true regarding restriction endonucleases?
A. They are called molecular scissors.
B. These are the enzymes responsible for restricting the growth of bacteriophages in E. coli.
C. They cut the DNA only at the centre of the palindromic sites.
D. They remove nucleotides only from the ends of DNA fragments.
E. They recognise specific palindromic base-pair sequences.
Choose the answer from the options given below :
- A
A and B only
- B
A and E only
- C
D and E only
- D
C and D only
Restriction endonucleases usually cut DNA slightly away from the centre of the palindromic site, so statement C is wrong. They do not remove nucleotides from the ends of DNA fragments — that is the role of exonucleases — so statement D is also wrong. Hence statements C and D are not true.
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