Multiple choice

Which of the following statements is/are correct about the structure of deoxyribonucleic acid?

  1. It is made of two polynucleotide chains, where the backbone is constituted by sugar-phosphate, and the bases project outside.
  2. The two chains have anti-parallel polarity.
  3. Adenine forms three hydrogen bonds with thymine from opposite strand.
  4. The two chains are coiled in a right-handed fashion.

  1. 1 and 2

  2. 1 and 4

  3. 2 and 3

  4. 2 and 4

  5. 3 and 4
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The two chains have anti-parallel polarity. It means, if one chain has the polarity 5'→3', the other has 3'→5'. The two chains are coiled in a right-handed fashion. The pitch of the helix is 3.4 nm and there are roughly 10 bp in each turn. Consequently, the distance between a bp in a helix is approximately equal to 0.34 nm.

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