Question

Methylated DNA doesn’t form kink as________________

(a) As they don’t fit in the active site

(b) The enzyme recognized methylated A as different base than non-methylated A

(c) They are less flexible so no kink is formed

(d) They don’t interact with the side chains in an active site

This question was posed to me in my homework.

This intriguing question comes from Restriction Endonuclease topic in division Genomics : The Mapping and Sequencing of Genomes of Cytogenetics

Answer 1

The correct option is (d) They don’t interact with the side chains in an active site

To explain: The kink in the DNA is formed not by just the recognition of the base sequence in the restriction site, but also by the interactions of the side chains. Asp 185 is unable to interact with methylated A, so no kink is formed.