​​Subtopic 1.6: RNA


RNA stands for ribonucleic acid.
RNA molecules are single strands.

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RNA components:
  • Sugars - Ribose
  • Phosphates -  (PO4−3)
  • Base:  cytosine (C), guanine (G), adenine (A) and uracil (U)


RNA molecules often form secondary (2°) structures and may interact with DNA, other RNA molecules, and proteins. These interactions help to define the particular function of each type of RNA.


Types of RNA molecules and functions:
  • Messenger RNA (mRNA): molecules which function as the transmitter of genetic information from the DNA genetic code to the resulting protein.
  • Transfer RNA (tRNA): molecules that carry amino acids and match them with a specific mRNA sequence during protein synthesis.
  • Ribosomal RNA (rRNA): molecules associated with proteins and are responsible for the synthesis of protein molecules.
  • Regulatory RNA: molecules involved in regulation of DNA expression, posttranscriptional mRNA processing, and the activity of the transcribed mRNA message.
Picture
Figure 15. Basic structure of RNA
Picture
Figure 16. Structure of DNA and RNA

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The basic structure of DNA and RNA are similar, however with 3 main differences:

1. Three of the nitrogenous bases are the same in the DNA and RNA: adenine, cytosine, and guanine. The fourth base for DNA is thymine while for RNA is uracil.

2. The DNA molecule is usually double stranded and most cellular RNA molecules are single stranded.

3. In the DNA molecule the sugar is deoxyribose and in the RNA molecule the sugar is ribose