How Illumina Methylation Array Find Out Whether It Is A Tg In Original Sample

Question

[ruansun1983]

Illumina methylation 450k detect methylation by converting CG -> TG through bisulfite treatment. Then it detects the signal strength of CG (methylated intensity) versus TG (unmethylated intensity) But what if the site is originally TG? I mean TG without bisulfite treatment.

Answer 1

[Neilfws]

Short answer: the probes on the Illumina 450K platform are designed to examine CpG sites. TG sites are of no interest, since they cannot be methylated.

You should read the details of how the platform was designed - starting point.

[ruansun1983]

You didn't quite understand my question. I mean how can they make sure the site is CpG, not TpG in specific sample?

[Neilfws]

You don't quite understand my answer. They are sure the site is CpG because the probes on the 450K platform are designed to target CpG sites, not TpG sites.