NEETZoologyBiotechnology - Principles and Processes
Which of the following representations correctly shows the palindromic sequence and the exact cleavage sites (indicated by arrows) for the restriction endonuclease EcoRI?
Options
- A5' G A A T T C 3' 3' C T T A A G 5'
- B5' G A A T T C 3' 3' C T T A A G 5'
- C5' G A A T T C 3' 3' C T T A A G 5'
- D5' G A A T T C 3' 3' C T T A A G 5'
Correct answer
D. 5' G A A T T C 3' 3' C T T A A G 5'
Step-by-step solution
EcoRI recognizes the 6-base pair palindromic sequence 5' - G A A T T C - 3'. It does not cut exactly in the center of the palindrome (which would produce blunt ends). Instead, it cuts between the same two bases on the opposite strands, specifically between the G and A bases. This staggered cut generates overhanging stretches called sticky ends. Therefore, the correct cleavage site is between G and A on the 5' 3' strand, and between A and G on the 3' 5' strand. Answer: 5' G A A T T C 3' 3' C T T A A G 5'