Chemistry Liquids MDCAT 2019
PMDC Verified Question 62 of 73
According to Watson and Crick's model of DNA, the DNA molecule consists of a double helix. What type of forces are responsible to keep two strands of DNA together?
A
Hydrogen bonding
B
Van der Waal's forces
C
Ionic bonding
D
Dipole-induces dipole forces
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option A: Hydrogen bonding
Concept:

The Watson-Crick DNA model dictates that two antiparallel polynucleotide strands wind around a common axis, held together by specific base pairing.

Formula:

Not applicable.

Solution:

  • The core stabilization of the DNA double helix comes from complementary nitrogenous bases on opposing strands.


  • These bases interact via Hydrogen Bonds. Adenine pairs with Thymine via 2 H-bonds, and Guanine pairs with Cytosine via 3 H-bonds.


Why other options are incorrect:

Van der Waals forces assist vertically (base stacking), but the horizontal linkage strictly keeping the two separate strands tied together is hydrogen bonding. Ionic bonds occur in salt crystals, not organic base pairing.

Quality & Fidelity Assurance: Every question on BeambePrep is rigorously curated against the official PMDC syllabus with zero filler, zero out-of-syllabus content, and zero typos. When an authentic past paper originally contained a historical mistake or ambiguity from the examining board (such as UHS or NUMS), BeambePrep faithfully reflects the original paper while detailing the nuance and scientific consensus in the autopsy above.

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