Here's why:
* Hydrogen bonds are weak, electrostatic interactions between a hydrogen atom covalently linked to a highly electronegative atom (like oxygen or nitrogen) and an electron pair in the adjacent atom.
* These bonds are perfect for holding the two strands of DNA together because:
* They are weak enough to allow the DNA to be easily unwound and replicated, but
* They are strong enough to maintain the double helix structure under normal conditions.
* Adenine (A) on one strand pairs with thymine (T) on the opposite strand using two hydrogen bonds.
* Guanine (G) on one strand pairs with cytosine (C) on the opposite strand using three hydrogen bonds.
So, these hydrogen bonds, though individually weak, collectively contribute to the stability of the DNA double helix.
