At the physiological pH the DNA molecules are:
**Core Concept**
DNA molecules have a negative charge due to the presence of phosphate groups in their backbone. The physiological pH of the human body is slightly alkaline, ranging from 7.35 to 7.45. This pH affects the overall charge of DNA molecules.
**Why the Correct Answer is Right**
At physiological pH, the phosphate groups in DNA are deprotonated, resulting in a net negative charge. This is because the pKa of the phosphate group is around 1.5 to 2.5, and at physiological pH, the group is predominantly in its deprotonated form. The negative charge of DNA molecules is crucial for their interaction with positively charged molecules, such as histones, and for their movement through the cell.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is not provided.
**Option B:** This option is not provided.
**Option C:** This option is not provided.
**Clinical Pearl / High-Yield Fact**
DNA molecules are highly negatively charged due to the presence of phosphate groups in their backbone. This charge is crucial for their interaction with positively charged molecules and for their movement through the cell. Understanding the charge properties of DNA is essential for understanding various cellular processes, including DNA replication and transcription.
**Correct Answer: C. Negatively charged.**