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Old 02-25-2014, 04:32 PM   #8
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Location: USA

Join Date: Jan 2012
Posts: 8

I can't comment on the T issue. No clue either. As for more than 5 bases, there are hordes of different modified bases that vary with species. In humans 5meC is most common but that is not true for all species. The next most common in humans is probably 5hydroxymethylC. PCR obscures this because the history of modification is lost when the DNA is copied multiple times during PCR. Single-molecule systems like PacBio or Oxford can, in theory and sometimes in practice, detect some of these because the modified bases are detected or copied directly. As for multiple cells being used for sequencing, that does not eliminate the need for PCR with non-single-molecule systems because each molecule has to be identical but each cell's DNA will break in unique ways. PCR is needed to make the ends the same. And yes, this can and does introduce issues with amplification bias and sometimes copying errors.
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