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Salient Features of Double-Helix Structure of DNA - Practice Questions & MCQ

Edited By admin | Updated on Sep 18, 2023 18:34 AM | #NEET

Quick Facts

  • Salient Features of Double-Helix Structure of DNA is considered one of the most asked concept.

  • 18 Questions around this concept.

Solve by difficulty

The hemagglutinin protein in influenza virus contains a long alpha helix, with 53 residues. Which of the following correctly describes the attributes of this alpha helix?

Which one of the following statements on nucleic acids is not true?


 

 

Concepts Covered - 1

Salient Features of Double-Helix Structure of DNA
  • It is made of two polynucleotide chains, where the backbone is constituted by sugar-phosphate, and the bases project inside.
  • The two chains have antiparallel polarity. It means if one the chain has a polarity of 5'-3', the other has 3'-5'.
  • The bases in two strands are paired through hydrogen bond (H-bonds) forming base pairs (bp). 
  • Adenine forms two hydrogen bonds with Thymine from the opposite strand and vice-versa.
  • Similarly, Guanine is bonded with Cytosine with three H-bonds.
  • As a result, always a purine comes opposite to a pyrimidine. 
  • This generates approximately uniform distance between the two strands of the helix. 
  • The two chains are coiled in a right-handed fashion. 
  • The pitch of the helix is 3.4 nm (a nanometre is one-billionth of a metre, that is 10-9 m) and there is roughly 10 bp in each turn.
  • The distance between a bp in a helix is approximately equal to 0.34 nm.
  • The plane of one base pair stacks over the other in the double helix. This, in addition to H-bonds, confers stability of the helical structure.

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Salient Features of Double-Helix Structure of DNA

Biology Textbook for Class XII

Page No. : 97

Line : 30

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