Here's why:
* Base Pairing: The two strands of DNA are held together by complementary base pairing. Adenine (A) always pairs with thymine (T), and guanine (G) always pairs with cytosine (C).
* Hydrogen Bonds: These base pairs are linked by hydrogen bonds. A hydrogen bond is a weak electrostatic interaction between a hydrogen atom covalently linked to a highly electronegative atom (like oxygen or nitrogen) and an electron pair in a nearby atom. These weak bonds are numerous and collectively contribute to the stability of the DNA double helix.
Important Note: While hydrogen bonding is the primary force holding the two DNA strands together, there are also other interactions contributing to the stability of the double helix, such as:
* Van der Waals forces: Weak, short-range attractive forces between molecules due to temporary fluctuations in electron distribution.
* Hydrophobic interactions: The nonpolar bases tend to stack on top of each other, minimizing contact with water.
However, it's important to remember that hydrogen bonding is the key interaction responsible for the stability and specific pairing of the two strands of DNA.
