DNA has what overall electrical charge?

DNA has what overall electrical charge?

• A. Positively charged
• B. Negatively charged
• C. Neutral
• D. Slightly positive

Answer: (B)

DNA carries an overall negative charge because its sugar-phosphate backbone contains phosphate groups that are ionized to carry negative charges at physiological pH. With many phosphates along the length of the molecule, DNA becomes a polyanion—the cumulative negative charges along the backbone dominate, while the bases themselves contribute little net charge. Positive ions in solution can shield some of this charge, but they don’t reverse the sign. This negative charge explains why DNA migrates toward the positive electrode in gel electrophoresis and interacts with positively charged proteins in chromatin.

DNA carries an overall negative charge because its sugar-phosphate backbone contains phosphate groups that are ionized to carry negative charges at physiological pH. With many phosphates along the length of the molecule, DNA becomes a polyanion—the cumulative negative charges along the backbone dominate, while the bases themselves contribute little net charge. Positive ions in solution can shield some of this charge, but they don’t reverse the sign. This negative charge explains why DNA migrates toward the positive electrode in gel electrophoresis and interacts with positively charged proteins in chromatin.