Question

Which of the following are correct about EcoRI?

A. Cut the DNA with blunt end

B. Cut the DNA with sticky end

C. Recognise a specific palindromic sequence

D. Cut the DNA between the base G and A when encounters the DNA sequence ‘GAATTC’

E. Exonuclease

Choose the correct answer from the options given below:

(1) B, C, E only

(2) A, D, E only

(3) A, C, D only

(4) B, C, D only

Answer 1

Correct option is (4) B, C, D only

EcoRI does not cut the DNA with blunt ends. Instead, it cuts the DNA with sticky / cohesive / staggered ends on each strand.

EcoRI is a restriction endonuclease that recognises a specific palindromic sequence and cuts at a specific site within the DNA, known as the restriction site. It is not an exonuclease as exonucleases remove nucleotides from the free ends of the DNA.

The recognition sequence for EcoRI is 

\(5' - G^\downarrow - A - A - T-T-C-3'\\3' - C - T-T - A-A_\uparrow-G - 5'\)

and it cuts the DNA between bases G and A only when the sequence GAATTC is present in the DNA.

Therefore, ‘A’ and ‘E’ represent incorrect features about EcoRI, whereas ‘B’, ‘C’ and ‘D’ are correct features of EcoRI.

The other options, i.e., (A), (B) and (C) are incorrect as they represent incorrect combinations of features w.r.t. EcoRI.