[{"from": "human", "value": "Could you give me a brief overview of this molecule? [C][C][=C][Branch1][#Branch2][N][C][=Branch1][C][=O][N][=C][Ring1][#Branch1][N]"}, {"from": "gpt", "value": "The molecule is a methylated form of the nucleobase cytosine occurring predominantly in cytosine-phosphate-guanine (CpG) islands that are produced by DNA methyltransferases and may regulate gene expression. Like cytosine, the DNA sequence containing 5-methylcytosine (5-mC) is able to be replicated without error and 5-mC can pair with guanine in double stranded DNA. However, DNA sequences containing a high local concentration of 5-mC may be less transcriptionally active than areas with higher ratios of unmodified cytosine."}]