In the following palindromic base sequences of DNA, which one can be cut easily by particular restriction enzyme?
- 5'GATACT3' ; 3'CTATGA5'
- 5'GAATTC3' ; 3'CTTAAG5'
- 5'CTCAGT3' ; 3'GAGTCA5'
- 5'GTATTC3' ; 3'CATAAG5'
Answer
(2) 5'GAATTC3' ; 3'CTTAAG5'
Solution
A palindromic sequence reads the same on both strands when read in the same orientation (5' 3').
(1) 5'GATACT3'; other strand 5' 3': AGTATC ⇒ not palindromic.
(2) 5'GAATTC3'; other strand 5' 3': GAATTC ⇒ palindromic.
(3) 5'CTCAGT3'; other strand 5' 3': ACTGAG ⇒ not palindromic.
(4) 5'GTATTC3'; other strand 5' 3': GAATAC ⇒ not palindromic.
As per NCERT, 5'GAATTC3' / 3'CTTAAG5' is the recognition sequence of EcoRI, which cuts it between G and A.
Answer: (2)