RNA

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RNA or ribonucleic acid is a polymer consisting of nucleotide monomers. They contain the base uracil rather than thymine and ribose rings rather than deoxyribose rings as compared to DNA. RNA is transcribed from DNA by RNA polymerases. It is important as the template for the synthesis of proteins by translating genes, to enable the transfer of amino acids to the ribosome in the right order, to synthesize the required protein.

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Chemical structure

RNA has three bases in common with DNA. These are adenine, guanine and cytosine. The one base that differs from DNA is uracil. Uracil through similar to thymine is less expensive to produce and this may be the reason for its use in RNA. Although cheaper to produce energy wise, this base is most probably not used in DNA as cytosine can degrade to this base. Thus the use of thymine makes detection of this degradation easier and facilitates repair. So its use in RNA is appropriate as the issue of lifespan is not in question but rather quantity versus DNA where the sequence must be maintained.

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Synthesis

RNA synthesis is catalyzed by an enzyme called RNA polymerase. This process uses DNA as a template and synthesis starts with the binding of the enzyme to the DNA. This initiates the unzipping of the DNA double helix and the synthesis of a complementary RNA molecule.

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Biological roles

There are several types of RNA which all serve different biological functions. These include:

  • Messenger RNA or mRNA – This functions by carrying information from DNA to the ribosome areas of protein synthesis.
  • Transfer RNA or tRNA – This is a small RNA chain that serves to move a specific amino acid to a polypeptide chain that is being synthesized at a ribosome.
  • Ribosomal RNA or rRNA – This is part of the ribosomes which synthesize proteins in the cell.
  • Non-coding RNA or RNA genes – These are genes that encode RNA that is not translated into a protein.
  • Double-stranded RNA – This is RNA which has a complementary strand such as that found in DNA and this forms the genetic material of some viruses.
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