:RNA may also stand for the Republic of New AfricaRibonucleic acid (RNA) is a nucleic acid consisting of a string of covalently-bound nucleotides. It is biochemically distinguished from DNA by the presence of an additional hydroxyl group, attached to each pentose ring; as well as by the use of uracil, instead of thymine. RNA transmits genetic information from DNA (via transcription) into proteins (by translation).
1 Chemical structure
RNA with its nitrogenous bases to the left and DNA to the right.
RNA has four different bases: adenineAdenine is one of the two purine bases used in forming nucleotides of the nucleic acids DNA and RNA. In DNA, adenine (A) binds to thymine (T) to assist in stabilizing the nucleic acid structures. In RNA, adenine binds to uracil (U). Adenine forms adenosin, guanineGuanine (2- amino-6- oxy purine) is one of the four main nitrogenous bases found in nucleic acids (e. DNA and RNA). Guanine is a purine derivative and in Watson-Crick base pairing forms hydrogen bonds with cytosine. The nucleoside is called guanosine., cytosineCytosine is one of the 5 main nitrogenous bases used in storing and transporting genetic information within a cell. It is a pyrimidine derivative, with a heterocyclic aromatic ring and two substituents attached (an amine group at position 4 and a keto gro, and uracil. The first three are the same as those found in DNA, but uracil replaces thymine as the base complementary to adenine. This may be because uracil is energetically less expensive to produce, although it easily degenerates into cytosine. Thus, uracil is appropriate for RNA, where quantity is important but lifespan is not, whereas thymine is appropriate for DNA.
2 Comparison to DNA
Structurally, RNA is indistinguishable from DNA except for the critical presence (noted above) of an additional hydroxyl group attached to the pentose ring in the 2'Molecular biologists use several shorthands when referring to nucleic acid molecules such as DNA and RNA, collectively referred to as nucleic acid nomenclature . The most common is the representation of the base pairs as letters an adenine nucleotide is a position. This additional group gives the molecule far greater catalytic versatility and allows it to perform reactions that DNA is incapable of performing; but at the same time, it makes RNA sensitive to alkaline hydrolysis, to which DNA is not.
The other major difference between RNA and DNA is that RNA is almost exclusively found in the single-stranded form (an exception being the genetic material of some kinds of viruses). RNA molecules often fold into more complex structures by making use of complementary internal sequences; that is, one part of a single RNA molecule is the nucleic acid complement of another part of the same molecule (for example, 5'-ACUCGA- 3' and 5'-UCGAGU-3'), so that the two strands bind together. This allows the formation of hairpin loops, coils, etc., which then direct the formation of higher-order structures.
3 RNA world hypothesis
The RNA world hypothesis proposes that the universal ancestor to all life relied on RNA both to carry genetic information like DNA and to catalyze biochemical reactions like an enzyme. In effect, RNA was, before the emergence of the first cell, the dominant, and probably the only, form of life. This hypothesis is inspired by the fact that retroviruses use RNA as their sole genetic material, while peptide bond formation in the ribosome is carried out by an RNA-derived ribozyme. From this perspective, retroviruses and ribozymes are remnants, or molecular fossils, left over from that RNA world. Assuming that DNA is better suited for storage of genetic information and proteins are better suited for the catalytic needs of cells, one would expect reduced use of RNA in cells, and greater use of DNA and proteins.
