In certain bacteriophages, 5- methylol cytosines have substituted for the cytosine. In the late 40s, looks up Garv E.

To make Z-DNA typically requires a stretch of alternating cytosine and guanine bases.

The methyl groups are attached only to specific cytosine bases - one of the four building blocks of DNA.

Currently, the most active area of research involves introducing one of the cytosine genes into the cancer cell.

It or its corresponding nucleoside or nucleotide may be prepared from DNA by selective techniques of hydrolysis.