Structure of DNA

Structure of DNA

  • DNA is formed by the joining of many nucleotides. These nucleotides are called monomers.
  • Phosphate and sugar in DNA are linked together by ester bonds. It is arranged in an alternate order.
  • Nitrogen bases are linked to each other by H-bonds and to sugars by glycosidic bonds.
  • Nitrogen bases are arranged on top of each other in the form of a layer to form a polynucleotide chain.
  • The following types of structures are possible in DNA.

1. Primary Structure –

  • In this, nucleotides are joined by phosphodiester bonds to the 5′ and 3′ carbon molecules.
  • In this, the chain is represented by the first letter of the base. Whose 5′ end is towards Left.
  • Ex. – A-G-C-T-T-A-C-A

2. Secondary Structure

  • In this, bases of ssDNA (Primary Structure) are joined by hydrogen bonds with bases of other ssDNAs. From which dsDNA is formed.
  • Nucleotides in this DNA join at special bond angles to form a spiral structure.

3. Tertiary Structure –

  • In this, the dsDNA becomes hypercoiled to form a 3D structure.
  • The double helix chain of DNA is tertiary structure, which is found in different forms.

4. Quaternary Structure –

  • The tertiary structure becomes hypercoiled again. Due to which Nucleoprotein and Nucleosome are present.
  • It again forms a super coiled structure by forming a loop. Which is called chromatin.

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