1. Which one of the following interactions plays a major role in stabilizing B-DNA?

   (1) Hydrogen bond
   (2) Hydrophobic interactions
   (3) Van der Wall’s interactions
   (4) Ionic interactions

Comprehending B-DNA Stability: The Crucial Interaction

Under physiological conditions, DNA, the genetic blueprint of life, is mostly found in the B-form. One of the many interactions that support its structural stability is crucial to preserving the double helix’s integrity.

Hydrogen Bonds’ Function in B-DNA Stability

Hydrogen bonds are the most important interaction that stabilises B-DNA. The specificity of base pairing is guaranteed by these bonds, which form between complementary nitrogenous bases (guanine-cytosine and adenine-thymine). The two DNA strands are held together by hydrogen bonds, which also give biological processes like transcription and replication flexibility.

Additional Factors Affecting DNA Stability

Other molecular interactions are also important, even though hydrogen bonds are the main stabilising force:

1. Hydrophobic Interactions

Because they are hydrophobic, DNA’s nitrogenous bases steer clear of water. As a result, bases are stacked inside the helix, protecting them from the watery surroundings. The overall stability of B-DNA is greatly enhanced by this base stacking.

2. Interactions of Van der Waals

Van der Waals forces encourage the close packing of stacked bases, which further stabilises B-DNA. The DNA molecule receives significant structural support from the sum of these weak interactions.

3. Interactions of Ionics

Because of the negative charge on the phosphate backbone of DNA, strands may repel one another. Positively charged ions, like Mg²⁺ and Na⁺, counteract these repulsions, maintaining structural integrity. Ionic interactions contribute, but they are not the main stabilising factor.

Conclusion: The Essential Stabiliser Is Hydrogen Bonding

The most important of these interactions for preserving B-DNA stability is hydrogen bonding. The double helix would lose its unique base-pairing rules in the absence of hydrogen bonds, which would cause structural collapse. Nonetheless, the robustness of DNA in living things is guaranteed by the interaction of Van der Waals forces, hydrophobic interactions, and hydrogen bonds.

Researchers can better investigate genetic stability, DNA replication mechanisms, and even the design of targeted therapies in molecular biology by comprehending these interactions.

Final Answer: The interaction that plays the major role in stabilizing B-DNA is hydrogen bonding.