The genes of viruses can be made of both DNAs and RNAs, contrasting to plants and animals which must only be made of DNAs. The distinction between DNAs and RNAs is the interchangeability of 2 genetic bases namely between uracil and thymine. Thymine can be found only in DNAs while uracil can be found only in RNAs. Viral genes may consist of double stranded DNAs, single stranded DNAs, double stranded RNAs, or single stranded RNAs. These are usually organized as a single linear or circular molecule of nucleic acid. The smallest viruses have only 4 genes, while the largest have several hundred.

At the molecular level, the difference between DNAs and RNAs is one single methane molecule (CH₄) with 2 missing hydrogen bonds (CH₂). These are always missing in RNAs but not in DNAs. Double stranded DNAs are always composed of equal proportion of adenine to that of thymine, and equal proportion of guanine to that of cytosine. Since both adenine and guanine are classified as purines while cytosine and thymine are both classified as pyrimidines, the proportion of purines to that of pyrimidines in DNAs are also always equal. However, since the thymine in DNAs is replaced by the uracil in RNAs, the chemical compositions of both dictate their differences. The molecular formula of thymine is C₅H₆N₂O₂ and that of uracil is C₄H₄N₂O₂. Clearly, uracil is short 1 carbon and 2 hydrogen atoms. It can be hypothesized that for want of this methane molecular ion (CH₂) is reason why RNA viruses are destructive to living cells. To neutralize infectious RNA viruses is simply to expose them to dissolved CH₂ solutions. On the other hand, it can also be hypothesized that all DNA viruses are beneficial. They can transcribe the intelligence enhancing proteins of prions. As hypothesis, modified CH₂ solutions can be used to treat or to destroy different forms of cancer cells, which certainly must be the progeny of RNA viral genes.