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:

Solution & Explanation

Answer: (4) C and D only Solution: The statements NOT true are C and D. Restriction endonucleases cut DNA a little away from the centre of the palindromic site (not exactly at the centre), so C is false; removing nucleotides only from the ends of DNA is the property of exonucleases, not restriction (endo)nucleases, so D is false. Statements A (molecular scissors), B (restrict bacteriophage growth in E. coli) and E (recognise palindromic sequences) are all true. The given key 'D' corresponds to option (4). NCERT Reference: Ch 9, p.167, line(s) 8 — "Restriction enzymes cut the strand of DNA a little away from the centre"