The Question is from neet-botany , and it was created by the author Mr. NARESH KUMAR K

Question

Which factor significantly contributes to the stability of the DNA double helix, in addition to hydrogen bonding between bases?

Mr. NARESH KUMAR K · Accepted Answer

## CORE INFORMATION
✓ **Answer**: B
## CONCEPT FRAMEWORK
 **Primary Concept**: DNA structure and stability
 **Related Topics**: Hydrogen bonding, hydrophobic interactions, van der Waals forces
 **Prerequisites**: Understanding of DNA double helix structure, base pairing (A-T, G-C)
## SOLUTION PATHWAY
**Given Information**:
The question asks for a factor contributing to DNA double helix stability *in addition* to hydrogen bonding between bases.
**Method & Steps**:
1. Consider the forces involved in DNA structure.
  Reasoning:  The DNA double helix is stabilized by multiple interactions. Hydrogen bonds between complementary bases (A-T and G-C) are crucial, but not the only contributor.
  Formula/Rule: No specific formula is needed for this question; it's conceptual.
2. Analyze the given options.
  Working: Let's examine each option:
  a) Repulsive forces between phosphate groups:  Phosphate groups are negatively charged and would repel each other, destabilizing the helix. This is incorrect.
  b) Base stacking interactions:  These are hydrophobic interactions between the aromatic rings of the bases.  These interactions are significant contributors to the stability of the double helix.
  c) Free rotation around the phosphodiester bond:  While some rotation occurs, it doesn't directly contribute to the *stability*.  Excessive rotation could destabilize the structure.
  d) Electrostatic attraction between sugars: Sugars are not directly involved in significant attractive forces that stabilize the DNA double helix. 
 3. Identify the correct factor.
  Result: Base stacking interactions (option B) are a major contributor to DNA stability, in addition to hydrogen bonding.
  Verification: Base stacking is a well-established principle in molecular biology explaining a significant portion of DNA stability. 
 ## OPTION ANALYSIS
A :x: Repulsive forces between phosphate groups are destabilizing, not stabilizing.
B ✓: Base stacking interactions are a major stabilizing force due to hydrophobic interactions and van der Waals forces between the stacked bases.
C :x: Free rotation around the phosphodiester bond is not a significant factor contributing to stability; it is more related to flexibility.
D :x: Electrostatic attraction between sugars is negligible in the context of overall DNA helix stability.
 ## LEARNING AIDS
 **Common Mistakes**:
  1.Focusing solely on hydrogen bonds:  Students may overlook the other important forces that contribute to DNA stability.
   How to avoid: Remember that multiple weak interactions collectively contribute to the overall strength of the DNA double helix.
  2.Misunderstanding the role of phosphate groups:  Students might incorrectly think that the negative charges of phosphates contribute to stability.
   How to avoid: Understand that the negative charges repel each other, requiring counterions (like Mg2+) for neutralization and stability.
 **Quick Tips**:
  1.Remember the hydrophobic nature of base stacking interactions.
  2.Think of the DNA double helix as a combination of hydrogen bonds and hydrophobic interactions working together for stability.

Mr. NARESH KUMAR K · Answer

Repulsive forces between phosphate groups

Mr. NARESH KUMAR K · Answer

The correct Option is "Base stacking interactions"

Mr. NARESH KUMAR K · Answer

Free rotation around the phosphodiester bond

Mr. NARESH KUMAR K · Answer

Electrostatic attraction between sugars

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