Lesson eLearning

Which of the following correctly describes the hydrogen‑bonding pattern in double‑stranded DNA?

easy MCQ 1 mark Class 12 · Biology · Molecular Basis of Inheritance
  1. A‑T pairs by two hydrogen bonds and G‑C pairs by three hydrogen bonds
  2. A‑T pairs by three hydrogen bonds and G‑C pairs by two hydrogen bonds
  3. A pairs with C and T pairs with G, each by two hydrogen bonds
  4. All base pairs have equal number of hydrogen bonds
Answer
A‑T pairs by two hydrogen bonds and G‑C pairs by three hydrogen bonds

The correct answer is A‑T pairs by two hydrogen bonds and G‑C pairs by three hydrogen bonds — Select the option that states this pattern correctly.

Step-by-step solution

  1. Identify the complementary base‑pairing rule in DNA.
  2. Recall that adenine (A) pairs with thymine (T) and guanine (G) pairs with cytosine (C).
  3. Remember that each A‑T pair is stabilized by two hydrogen bonds, whereas each G‑C pair has three hydrogen bonds.
  4. Select the option that states this pattern correctly.
Common mistake: Confusing A‑T with A‑G or assuming all pairs have the same number of bonds

Concept tested: Base‑pairing in DNA

Published · How this solution was prepared and checked

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