RNA (ribonucleic acid) is a biological signal molecule used to relay information from the cell's DNA to its protein making structures. While the "DNA to RNA to protein" pathway is one of RNA's key roles, many more have been discovered, and some RNA molecules have enzymatic properties and are known as ribozymes.
Comparison to DNA
The structure of DNA and RNA are similar but not identical. Both are built on a sugar-phosphate backbone that defines the polymer structure. RNA's sugar is ribose, while in DNA is it deoxyribose, which has one less oxygen. Three of the four bases used in the base sequence are identical, while RNA uses uracil where DNA uses thymine. Although many exceptions exist, DNA's native structure tends to be double stranded while RNA tends to be single stranded.