A sample collected by the Hayabusa 2 spacecraft from the spinning top-like asteroid contained the nucleobases adenine, guanine, cytosine, thymine, and uracil.

Targeted methylation of cytosine residues by S-adenosylmethionine–dependent DNA methyltransferases modulates gene expression in vertebrates. Here we show that cytosine-5-methyltransferases catalyze ...

Chemical structure of guanine, showing its double-ring purine structure and the functional groups involved in hydrogen bonding with cytosine. (Image: Public Domain) Guanine has the chemical formula ...

The DNA base cytosine has a lot of different outfits in its closet. Most famously, the base can slip on a methyl group at its fifth carbon, a change that lends cytosine the ability to silence genes.