And in every one of the 100 trillion cells, the sequence of these four letters ... small loops of DNA. We've now zoomed in enough to see portions of the DNA strand. The DNA is wrapped around ...

They form when stretches of cytosine letters on the same DNA strand pair with each other, creating a four-stranded, twisted structure protruding from the double helix. The researchers found that i ...

This deletion means that the letters shift, and the rest of the ... Slippage of the DNA template strand and subsequent insertion of an extra nucleotide is one example of a spontaneous mutation ...