RNA

RNA (ribonucleic acid) is a long molecule made up of a chain of nucleotides. Each nucleotide contains a ribose sugar, a phosphate group, and a nitrogenous base: adenine (A), guanine (G), cytosine (C), or uracil (U). Uracil in RNA replaces the thymine found in DNA.

RNA is typically single-stranded, which allows it to fold back on itself and form three-dimensional structures. Because of these structures, RNA is not merely an information storage molecule but can also perform chemical catalytic functions.

Major types

mRNA (messenger RNA) is copied from a section of DNA and then carries this information to the ribosome. tRNA (transfer RNA) brings the appropriate amino acid to each codon. rRNA (ribosomal RNA) is part of the ribosome structure and participates in linking amino acids together. There also exist small functional RNAs, such as microRNA and small nuclear RNA, which regulate the level of gene expression.

Role in gene expression

The central process of molecular biology is: DNA is transcribed to produce RNA, which is then translated into protein. Each three-base codon codes for one amino acid. Many viruses have RNA as their genetic material; some, such as retroviruses, use the enzyme reverse transcriptase to convert RNA into DNA.

Ribozymes and the RNA world hypothesis

Some RNA molecules, called ribozymes, function as enzymes, accelerating chemical reactions. This has led to the proposal of a hypothesis suggesting that early life on Earth relied on RNA to perform both functions—information storage and reaction catalysis—before DNA and proteins took on their present roles.

Technological applications

RNA is used in vaccines and treatments. mRNA vaccines provide cells with instructions to make a protein from a virus, allowing the body to prepare an immune response. RNA interference technology is also used to turn off specific genes, aiding research and treatment.