Question

Which of the following DNA sequences is the recognition site for EcoR I enzyme?

• A. 5’ GAATTC 3’
• B. 5’ GGATCC 3’
• C. 5’ AAGCTT 3’
• D. 5’ CAGCTG 3’

Answer 1

The correct option is A 5’ GAATTC 3’

Restriction enzymes are molecular scissors which are used to cleave phosphodiester bonds between consecutive nucleotides within specific DNA sequences known as recognition sequences.

Recognition sequences are generally palindromic. Palindromic sequences are sequences of base pairs in the DNA that reads the same on both the strands when the orientation of reading is kept the same.

EcoR I is a restriction enzyme that recognizes the following palindromic sequence and cleaves between G and A.
5' GAATTC 3'
3' CTTAAG 5'

5' GGATCC 3' is recognition sequence for BamH I

5' AAGCTT 3' is recognition sequence for Hind III

5' CAGCTG 3' is recognition sequence for Pvu II