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Salient Features of Double-Helix Structure of DNA MCQ - Practice Questions with Answers
Edited By admin | Updated on Sep 18, 2023 18:34 AM | #NEET
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Salient Features of Double-Helix Structure of DNA is considered one of the most asked concept.
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18 Questions around this concept.
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The two antiparallel strands in a DNA double helix are held together by :
The fact that a purine base is always paired through hydrogen bonds with a pyrimidine base leads to, in the DNA double helix
A single strand of nucleic acid tagged with a radioactive molecule is called:
NEET 2025: Syllabus | Most Scoring concepts | NEET PYQ's (2015-24)
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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