1. Which of the following base sequences would probably not be recognition sites for cleavage by
restriction endonucleases? Why not?
A. 5’ GAATTC 3’ B. 5’ CATTAG 3’ C. 5’ CATATG 3’ D. 5’ CAATTG 3’
The answer is B, I just can't figure out why. Can anyone please help me to understand? Thanks!
restriction endonucleases? Why not?
A. 5’ GAATTC 3’ B. 5’ CATTAG 3’ C. 5’ CATATG 3’ D. 5’ CAATTG 3’
The answer is B, I just can't figure out why. Can anyone please help me to understand? Thanks!
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When identifying restriction sites, what you are looking for is palindromes (words spelt the same both forward and backward). For example, look at option A: 5'-GAATTC-3'. The complement of this would be 3'-CTTAAG-5'. Now, read this complement in the 5' to 3' direction. What you get is 5'-GAATTC-3'. Notice anything? Its the exact same as option A. Option A would be a palindrome since its compliment is the exact same sequence of base pair if read in the same direction. The same goes for options C and D. Option B is the only one that is not a palindrome, so it would be the one that would most likely not be a restriction site.