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|The science of life|
RNA stands for ribonucleic acid, a polymer produced by all living things to help translate genetic information stored in DNA into functional proteins. It is single stranded and chemically different from DNA, replacing thymine with uracil and the sugar deoxyribose with ribose in its molecular backbone.
RNA comes in different types. Messenger RNA contains the genetic code, copied from DNA, that will determine which amino acids will be assembled to produce a specific protein. Ribosomal RNA forms part of the structure to assemble these proteins, and Transport RNA brings the amino acids needed to make the protein form. There are other types that help regulate the genetic processes of the cell.
 Possible Role in the Formation of Life
RNA structures store information, and certain types (called ribozymes) are able to manipulate other strands of RNA or assemble proteins out of amino acids. Short sequences can also replicate themselves if certain substances are present in the environment, and these compounds have been shown to form under the natural conditions that dominated the primitive earth. These characteristics may mean that RNA had a role in the formation of life.
One prominent theory states that RNA began to assemble itself into small, fragile strands. Most of them would fall apart under the harsh conditions of the time, but some would have been able to effectively reproduce themselves. Through random structural changes, some of those might have started assembling proteins from the amino acids floating in the sea, creating a self-replicating RNA-protein complex. If these proteins helped the strand to effectively reproduce, they would be kept and enhanced by natural selection, eventually leading to the formation of lone proteins more effective at reproduction than RNA or its complexes.