Researchers identify seventh and eighth bases of DNA

July 25, 2011 by Editor

New 5fC and 5caC bases (credit: Shinsuke Ito et al.)

Researchers from the University of North Carolina (UNC) School of Medicine have identified the seventh and eighth bases of DNA.

For decades, scientists have known that DNA consists of four basic units — adenine, guanine, thymine, and cytosine. In recent history, scientists have expanded that list from four to six.

Much is known about the “fifth base,” 5-methylcytosine, which arises when a chemical tag or methyl group is tacked onto a cytosine. This methylation is associated with gene silencing, since it causes the DNA’s double helix to fold even tighter upon itself. Last year, the researchers found that Tet proteins can convert 5 methylC (the fifth base) to 5 hydroxymethylC (the sixth base) in the first of a four-step reaction leading back to cytosine./.../