RNA and Central Dogma


  • While DNA encodes instructions to build life, RNA molecule read and act on the information.
  • It simply copies the instruction and carry it to other parts of the cells to make proteins.
  • Recent understanding has shown RNA has much bigger role than acting as a messenger. (more on this later)
  • In terms of molecule, the only difference in RNA is an extra OH group which makes is unstable.
  • Thus, the major difference between DNA and RNA is that while DNA is more permanent RNA is not permanent.

Central Dogma

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The central dogma of molecular biology explains
  • The central dogma of molecular biology explains the how genetic information flows from DNA to proteins.
  • This simply describes how the code of life is brought to life.
  • This happens in two-stages called transcription and translation.
  • In short DNA is transcribed into RNA which is then read by ribosome to make Proteins which are the building blocks of life.
  • Note that advancements in biotechnology coincide with the increased understanding of the central dogma.

Central dogma (cookbook analogy)

Central dogma (cookbook analogy)
  • Consider DNA to be a cookbook of recipes for making proteins. Transcription is the process of photocopying the recipe. This is done by mRNA, short for messenger RNA, inside the nucleus.
  • Once copied the recipe mRNA goes outside the nucleus to the chef, called ribosome.
  • There is also a translator, tRNA who translates mRNA recipe to rRNA of the ribosome which then makes amino acids, the building blocks of proteins.
  • A block of 3 letters in the mRNA correspond to ‘cooking’ of 1 amino acid.
  • Each 3-letter base in mRNA that is read by tRNA that correspond to one amino acid is called ‘codon’.
  • Many amino acids come together to form the primary structure of protein.
  • The primary structure is twisted and folded to make a 3-d structure of protein.


transfer RNA (tRNA) diagram
  • The coding part of protein are called as genes.
  • According to recent understanding there are about 20500 genes in human genome.
  • Genes vary in complexity. They range in size from few hundred bases to more than 2 million.
  • 98% of the genome is non-coding regions.
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