Two strands of the DNA are joined by:
**Core Concept**
The double-stranded structure of DNA is maintained by a specific type of covalent bond between the two strands. This bond allows for the replication and transmission of genetic information from one generation of cells to the next.
**Why the Correct Answer is Right**
The two strands of DNA are joined by hydrogen bonds between the base pairs. Adenine (A) forms a hydrogen bond with thymine (T), while cytosine (C) forms a hydrogen bond with guanine (G). This base pairing is specific and determines the sequence of nucleotides in the DNA molecule. The hydrogen bonds are relatively weak compared to the covalent bonds within the sugar-phosphate backbone, allowing for the easy separation of the two strands during replication.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect as it does not specify a type of bond that joins the two strands of DNA.
* **Option B:** This option is incorrect as it refers to a type of bond that is not relevant to the joining of DNA strands.
* **Option C:** This option is incorrect as it refers to a type of bond that is not responsible for joining the two strands of DNA.
**Clinical Pearl / High-Yield Fact**
The base pairing between A-T and C-G is a fundamental principle of molecular biology and is essential for understanding the structure and function of DNA. This concept is crucial for understanding genetic inheritance, mutation, and disease.
**Correct Answer: D. Hydrogen bonds.**