The two strands of DNA are held together by –
**Core Concept**
DNA is a double-stranded molecule, and the two strands are held together by specific interactions between the nucleotide bases. This is known as the double helix structure of DNA. The double helix is stabilized by hydrogen bonds between the bases, which are paired in a specific manner.
**Why the Correct Answer is Right**
The correct answer is due to the complementary base pairing between the two strands of DNA. Adenine (A) pairs with thymine (T) through two hydrogen bonds, while guanine (G) pairs with cytosine (C) through three hydrogen bonds. This base pairing is responsible for the double helix structure of DNA and holds the two strands together. The sugar-phosphate backbone of DNA provides additional structural support, but it is the base pairing that is primarily responsible for holding the two strands together.
**Why Each Wrong Option is Incorrect**
* **Option B:** This option is incorrect because it does not specify the correct mechanism of base pairing that holds the two strands of DNA together.
* **Option C:** This option is incorrect because it does not accurately describe the interactions between the two strands of DNA.
**Clinical Pearl / High-Yield Fact**
It's essential to remember that the base pairing between DNA strands is specific and follows the rules of complementary base pairing: A-T and G-C. This is a fundamental concept in molecular biology and is critical for understanding many biological processes, including DNA replication and transcription.
**Correct Answer:** C. Hydrogen bonds between the bases.