RNA Definition and Examples

RNA stands for ribonucleic acid , a biopolymer that encodes, decodes, regulates, and expresses genes . The forms in which RNA manifests itself can be as messenger (RNAm), ribosomal (RNAr) and transfer (RNAt). This biopolymer encodes the amino acid sequences to form proteins, that is, it is in charge of transcribing the DNA code to translate it into a specific protein with a function in the cell and the organism.

Thus, RNA participates in two of the processes of maintenance and expression of genetic information: the transcription of the genetic code (passage from a DNA language to an RNA language) and the translation of said code (passage from a language of nitrogenous bases). to another of amino acids, the units that make up proteins).

RNA structure and differences with DNA

Like DNA, RNA is made up of nucleotides based on a sugar, ribose (in DNA it is deoxyribose), which contains 5 carbon atoms: atom No. 1 unites with adenine, guanine, cytosine or the uracil when transcribed; however, it can be modified to include many other bases, including pseudouridine, ribothymidine, hypoxanthine, and inosine.

The connection of a phosphate group occurs at the carbon number 3 molecule of ribose and is attached to the carbon number 5 of the next molecule. RNA is electrically charged and there are hydrogen bonds between guanine and cytosine, adenine and uracil, as well as between guanine and uracil. As in DNA, nucleotides are the structural units that make up RNA chains, which are usually appreciably shorter than those of DNA.

Thanks to the additional hydroxyl in the ribose of RNA, RNA itself is more susceptible to chemical changes than in the case of DNA, because the activation hydrolysis energy is lower. The nitrogenous bases that RNA uses are guanine, thymine, adenine, and uracil ; on the other hand, DNA uses the same ones, but with thymine instead of uracil.

RNA is a single-stranded molecule, that is, it is made up of a single strand, unlike DNA, which is a double-stranded molecule . RNA, despite being single-stranded, tends to fold its chain helices by folding the molecule on itself in some sections. This gives it the ability to serve as a catalyst, in the same way that proteins resulting from translation can act as enzymes (biocatalysts).

RNA Types and Functions

It has already been mentioned that there are three types of RNA: messenger, transfer and ribosomal.

• Messenger RNA , represented as mRNA, is responsible for carrying information from the DNA to the ribosomes and there it is translated to produce proteins in the cell. This type of RNA is also considered coding since every three nucleotides form a codon and produce an amino acid. Amino acids join together and form proteins.

• Transfer RNA, represented as tRNA, is a short chain of at least 80 nucleotides that transfers a newly created amino acid to the end of a growing polypeptide (protein) chain. A molecule of this type of RNA contains a section that recognizes the amino acids in the messenger RNA.

• Ribosomal RNA, represented as rRNA, is associated with ribosomes, as the name suggests. In humans there are four types of rRNA; however, different types exist in other eukaryotic cells. This rRNA is synthesized in the nucleolus of the cell, passes to the cytoplasm, and there combines with proteins to form ribosomes.

On a large scale, these three types of RNA are the main ones. However, depending on its function in organisms, there are other types of RNA, such as:

• transference-message RNA , identified as tmRNA, which put the ribosomes that are stagnant back into operation; these are contained in the bacteria.
• Nucleolar RNA , identified as nRNA, which is an essential precursor to rRNA and is found in eukaryotic cells.
• Telomerase RNA , identified as TERC, is responsible for telomere synthesis, as its name implies, and is also found in eukaryotic cells.
• Promoter or enhancer RNA , which is involved in gene regulation.
• There is a type of parasitic RNA called a retrotransposon , as it propagates itself and is present in some eukaryotic cells.

Sources

Cañedo R., and Guerrero, J. (2005). Notions of biochemistry and genetics useful for information professionals in the health sector. ACIMED . Available at: http://ref.scielo.org/z8g4gy

Devlin M., T. (2019). Biochemistry with clinical applications. Spain: Reverte. Available at: books.google.co.ve/books?id=412U7jHov28C&dq