Which repair pathway would be used to repair a cytosine that has been turned into a uracil Group of answer choices nucleotide excision repair Base excision repair None of them. Uracil is a normal base so this is not a problem Mismatch repair

The repair pathway that would be used to repair a cytosine that has been turned into a uracil is Base excision repair.

Here's a step-by-step explanation:

1. In DNA, cytosine is one of the four nucleotide bases and uracil is not. Uracil is normally found in RNA. If a cytosine in DNA is mistakenly altered into a uracil, it's considered a DNA damage.

2. The Base Excision Repair (BER) pathway is specifically designed to correct small, non-helix-distorting base lesions from the genome. The process is initiated by DNA glycosylases, which recognize and remove specific altered bases, creating an apurinic/apyrimidinic site (AP site).

3. The AP site is then recognized by an AP endonuclease that cleaves the phosphodiester bond.

4. The resulting single-strand break can then be processed by either short-patch (where a single nucleotide is replaced) or long-patch BER (where 2-10 new nucleotides are synthesized).

5. In this case, the uracil would be recognized and removed by a specific DNA glycosylase (UNG - uracil-DNA glycosylase), and the resulting AP site would be processed by the BER pathway, effectively replacing the uracil with a cytosine.

So, the correct answer is Base excision repair.