5-base sequencing refers to the detection of five nucleotide bases in DNA, including the four standard bases (adenine, guanine, cytosine, and thymine) and a modified base, 5-methylcytosine (5mC), an important epigenetic marker.[1] In a typical DNA sequencing experiment, the epigenetic modification is lost during PCR amplification step and only the base forms of nucleotides are recognized.[2] In a 5-base sequencing based experiment, the information about methylation of cytosines is preserved through chemical or enzymatic modification allowing inference of methylation status during bioinformatics analysis.[3] More recently, nanopore or single-molecule realtime sequencing have enabled direct detection of methylated cytosines without any conversion of the DNA.[4][5]
The approach can further be extended to detect 5hmC modification, known as 6-base genome or sequencing.[2]
