The Roles Of Cellular RNA Biology Essay


RNA is ribonucleic acid and also a polymer of ribonucleoside-phosphates. Its backbone is comprised of alternating ribose and phosphate groups. RNA is single-stranded in that the RNA sugar ribose replaces deoxyribose and the nitrogenous base uracil replaces the thymine.RNA have a role in both storage and transmission of information and in catalysis. RNA molecules are associated with gene expression and are found in different forms within a given cell. The three major classes of cellular RNA molecules are: ribosomal RNA (rRNA), messenger RNA (mRNA), and transfer RNA (tRNA). rRNA,mRNA, and tRNA are formed from complementary copies of one of the two strands of DNA segments during the process of transcription. rRNA molecules are part of ribosome's (intra-cellular ribonucleoproteins that are the sites of protein synthesis).rRNA have two main functions it provides structure and shape producing the catalytic regions of the ribosome and also speeds up protein synthesis by interactions between tRNA and the protein synthesis machinery. Ribosomal RNA account for 80% of the total cellular RNA. tRNA are like carriers in which they carry amino acids to the ribosomes for incorporation into growing peptide chains during protein synthesis. tRNA account for 15% of the total cellular RNA and are 75-95 nucleotide residues long. mRNA molecules encode the sequence of amino acids in proteins. These carry information from DNA to the translation complex where proteins are synthesised. They account for only 3% of the total cellular RNA. These molecules are the least stable of the cellular ribonucleic acids. Another class of RNA are the small RNA molecules these are present in cells. They have a catalytic activity and contribute with proteins. Many of these molecules are associated with processing events that modify RNA after it has been synthesised (Horton.H, Perry.M, Morgan.L, Rawn.J, Scrimgeour.K, 2006)

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RNA have many roles in living cells such as they serve as temporary copies of genes that are used as templates for protein synthesis and also function to decode the genetic code and catalysing the synthesis of proteins. The molecule RNA is the only biological polymer that serves as both a catalyst (like proteins) and as information storage (like DNA). They use the information encoded in DNA to specify the amino sequence of a functional protein.RNA are found in both the nucleus and the cytoplasm.There were observations made that an increase in the protein synthesis is accompanied by an increase in the amount of cytoplasmic RNA and an increase in its rate of turnover. Observations led researchers to suggest that RNA carry genetic information from DNA to the ribosome. Francois Jacob and Jacques Monod proposed the name "messenger RNA"(mRNA) for the total cellular RNA carrying the genetic information from DNA to ribosomes, where the messengers supply templates that specify amino acid sequences in polypeptide chains. The process of forming mRNA on a DNA template is transcription. Transcription involves the following steps: A part of DNA unzips and hydrogen bonds between bases break and helix unwinds. This leads to free RNA nucleotides being placed against one of the exposed DNA strands. The nucleotides pair exactly as the RNA slot into place and form hydrogen bonds, condensation reactions happen between adjacent RNA nucleotides. Step by step a mRNA molecule is build up containing the gentic code. When the end of the gene is reached, the complementary mRNA molecule mRNA molecule breaks away. The mRNA molecule is then guided out of the nucleus through a pore in the nuclear envelope. This is passes into the cytoplasm and arrives at a ribosome. Messenger RNA is only the several classes of cellular RNA. Transfer RNA is another class of RNA ,these molecules are adaptor molecules in protein synthesis that are linked to an amino acid at one end, which pair with the mRNA in a way that amino acids are joined to polypeptide in the correct sequence. Transfer RNA play a role in translation. Translation is the process in which the code for making the protein is used to line up amino acids in a particular sequence, linking them together to make a polypeptide molecule. Each group of three consecutive bases in the mRNA is called a codon. Each codon codes for one amino acid. In translation tRNA takes part. There are 20 different kinds of tRNA. Each one has a group of three exposed bases called anticodon. An anticodon can undergo complementary base pairing with a codon. The mRNA molecule, carrying the code copied from part of a DNA molecule, is held in a cleft in the ribosomes so that six bases are exposed. A tRNA with an anticodon which exactly complements the first mRNA codon then binds with it. Complementary base pairing ensures that only the correct tRNA can bind. Another tRNA then binds with the next codon on the mRNA. mRNA moves through the cleft in the ribosome, bringing a third codon into place. A third tRNA binds with it and a third acid is made and added to chain. The first tRNA has completed its role and breaks way and the whole process is repeated and translation continues until the ribosome reaches a stop signal. (Nelson.D,Cox.M,2008)

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The statement 'RNA provides the link between biological information storage and biological function ' is justified as it functions in many ways as a carrier of genetic information, a catalyst of biochemical reactions, an adapter molecule in protein synthesis, and also in cellular organelles (sciencejrank,2009). RNA also take an important role in the ability of viruses to cause infection. RNA have an important role in guiding cells to where they are and its destination in the body this has been discovered to be true by researchers at Stanford University School of Medicine(eurekalert,2007). RNA are also known to facilitate protein-coding instructions from DNA to the cells meeting .

Taken from:Gate2Biotech,2009)