A cell can repair cytosine deamination damage, so it presumably has an enzyme th

Question

A cell can repair cytosine deamination damage, so it presumably has an enzyme that "recognizes" the product of this damage. The structural feature that this repair enzyme recognizes would most likely be: A1. A bulge in the duplex caused by cytosine deamination replacing a pyrimidine with a purine. A2. Non-planarity of the base, due to removal of the amine group. A3. Free radicals created by the cytosine deamination reaction. A4. C-rich sequences created by the cytosine deamination reaction. A5. None of the above would be plausible features recognized.

Explanation / Answer

In cytosine deamination, there is conversion of cytosine into uracil which is normally not a part of DNA.

So there is replacement of pyrimidine( cytosine) with a purine (uracil) and this is recognised by repairing enzyme (uracil DNA glycolase enzyme). The enzyme remove uracil and thus form abasic site.

Abasic site recognised by AP endonuclease which break phosphodiester bonds and thus add a new cytosine.

So answer is option A1.

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