What Is RNA Made Of?
Nucleic acids deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) are the genetic material of cells.
For eukaryotic cells (like you, me and everything except bacteria) DNA is the genetic blueprint that exists in the cells nucleus and has all the instructions for the structure and function of an organism. RNA is the nucleic acid that carries out the genetic instructions and ultimately translates the genetic blueprint into protein molecules.
Nucleic acids, whether DNA or RNA, are polymers (big molecules) made of smaller monomer subunits called nucleotides.
Nucleotides
Each monomer of nucleic acid, a nucleotide, consists of 3 portions:
- a pentose sugar
- one or more phosphate groups
- one of five cyclic nitrogenous bases
In nucleic acids, nucleotides are linked in a sugar-phosphate ‘backbone’ by covalent bonds between phosphate of one nucleotide and sugar of next, with nitrogenous bases extending from the backbone like teeth of a comb.
How Do Nucleotides Put Themselves Together Into Nucleic Acids?
Nucleotides are assembled into nucleic acids in an anabolic polymerization process.
- Anabolic = building bigger molecule
- Polymerization = taking monomers and putting them together into polymers (large molecules composed of many monomers).
Polymerization requires monomers (building blocks) and energy, and triphosphate deoxyribonucleotides provide both. These nucleotide building blocks of DNA bring their own energy for polymerization within their energy-rich phosphate bonds.
Types of RNA
Genetic information copied from DNA is transferred to 3 types of RNA:
Ribosomal RNA (rRNA) The Protein Factories
Most of the RNA in cells is associated with small cellular structures known as ribosomes, the protein factories of the cells. Ribosomes are the site of Translation, where mRNA arrives with genetic instructions for building proteins from amino acid monomers brought by tRNA.
Messenger RNA (mRNA) The Genetic Blueprint
Messenger RNA is a copy of the genetic information that was transcribed from the cell’s DNA. It is like a ‘blueprint’ of the genetic information and is brought to the ribosome and translated into protein with the help of tRNA.
Transfer RNA (tRNA) The Amino Acid Suppliers
Transfer RNA is part of the process of translation. It brings the amino acid coded for by mRNA, and these amino acids are joined together to form proteins.
What Does RNA Do?
Transcription
This is the process by which a DNA sequence is copied to produce a complementary RNA. In other words, it is the transfer of genetic information from DNA into RNA; like replication, but the nucleic acid RNA is made.
Transcription is the beginning of the process that ultimately leads to theTranslation of the genetic code into a peptide or protein.
Translation
Making proteins from instructions contained in the genetic code is called Translation. With the help of tRNA, ribosomes (which contain rRNA) make proteins from the message encoded in mRNA.
The genetic instructions for a polypeptide chain are ‘written’ in the DNA as a series of 3-nucleotide ‘words’ called codons. Each codon is the base triplet that encode for one amino acid. This is the ‘genetic code’.
Translation of the genetic code through the combined effort of rRNA, mRNA and tRNA ultimately results in the creation of polypeptide or protein.
More Information on Nucleic Acids
To learn more about nucleic acids, see the science website ScienceProfOnline or additional Suite101 articles, including Nucleotides & Nucleic Acids, Nucleic Acid Function, and Nucleic Acid Replication.
Sources
Bauman, R. (2005) Microbiology.
Park Talaro, K. (2008) Foundations in Microbiology.
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