What Is Ribonucleic Acid?

By Bridget Coila
Ribonucleic acid is one of the major molecules of all living cells.

Ribonucleic acid, also known as RNA, is one of the two major nucleic acids in the body. The other major nucleic acid is deoxyribonucleic acid, or DNA, which carries the genetic code of the cell. Together, these two molecules direct every activity in the body.


Ribonucleic acid has a backbone made up of a string of alternating phosphate groups and ribose molecules, which are a type of sugar. The ribose molecules each have a base attached to them. The four bases of RNA are adenine, uracil, cytosine and guanine. They differ from DNA only in that they have uracil instead of thymine, a difference that leaves RNA single stranded while DNA becomes a double-stranded helix.

Genetic Information

The basic function of RNA is to convert the genetic information contained in DNA into proteins that carry out all cell activity. In order to accomplish this, the cell must build a strand of RNA to match up exactly with the corresponding DNA strand. The guanine and cytosine molecules pair with each other, so every guanine base on the DNA is translated into a cytosine in the RNA strand and vice versa. Adenine in the DNA strand becomes uracil in the RNA strand and thymine in DNA pairs with adenine in RNA. A strand of RNA then directs the construction of a protein, with each amino acid of the protein corresponding to three bases on the RNA strand.

Main Types

There are several forms of ribonucleic acid. Messenger RNA, also called mRNAs, are created directly off of the DNA strand, so they are the direct mirror image of the DNA that created them. They carry the genetic information to the ribosomes, where protein synthesis takes place. Transfer RNA brings the amino acids, the basic components of the protein, to the ribosomes to be assembled there. The ribosomes are mainly made up of ribosomal RNA, which works to bind the amino acids together.

Alternate RNA Types

Viral RNA, or vRNA, operates in viruses to carry the genetic information of the virus and commandeer the protein-making apparatus of infected cells. Many small RNAs have been discovered that carry out active roles in the cell beyond the basic protein-creating function. Small nuclear RNA helps cut up mRNA strands into a manageable size. Micro RNAs help control gene expression by stopping protein production and small interfering RNAs prevent the formation of mRNAs. Other forms of RNA likely remain undiscovered and scientists continue to investigate possible activities and forms of this versatile molecule.