In: Chemistry
Your cells contain machinery to detect and repair DNA damage to protect the fidelity of your genetic code. One form of damage detected by this machinery is cytosine deamination. Explain why replacing the C4 amine in cytosine with a hydroxyl could result in an altered DNA sequence upon replication. Hint: consider tautomerism.
Please explain in as simple terms as possible. Thanks!
The replacement of C4-amine in the cytosine with a hydroxyl could result in an altered DNA sequence upon replication.
Explanation: In general, the cytosine molecule binds to DNA through nitrogen in the 4-position (C4-NH2) of the aromatic ring of cytosine. Now, i.e. after replacing the amine group, attached to C4 in the cytosine, by a hydroxyl group results in the tautomerism to form a new keto group in the 4-position and 2o amine (R2NH) in the 3-position of the aromatic ring of resulting molecule, which (NH in the 3-position) binds to DNA through the nitrogen. As a result, an altered DNA sequence takes place upon replication.
The detailed picture for the above explanation can be drawn as shown below.