Biotechnology: Principles and Processes

Which of the following cuts the DNA from specific places?

1. Exonuclease
2. Alkaline phosphatase
3. E. coli restriction endonuclease I
4. Ligase

Answer

(3) E. coli restriction endonuclease I

Solution

As per NCERT, restriction endonucleases make cuts at specific positions within the DNA; each recognises a specific palindromic nucleotide sequence.

∵ EcoRI (from E. coli RY 13) cuts DNA between G and A at the sequence GAATTC.

⇒ Exonucleases remove nucleotides only from the ends of DNA, alkaline phosphatase removes terminal phosphate groups and ligase joins DNA fragments.

∴ E. coli restriction endonuclease I cuts DNA at specific places.

Answer: (3)