Multiple Choice
Which set of nitrogenous bases is found in DNA?
30
views
7. DNA and Chromosome Structure
DNA Structure
Multiple Choice
In terms of overall electrostatic charge at physiological pH, what is the net charge of DNA and what structural feature is primarily responsible for it?
A
DNA is negatively charged primarily because the deoxyribose sugars are deprotonated.
B
DNA is positively charged because its nitrogenous bases carry a net positive charge.
C
DNA is negatively charged because its phosphate groups in the sugar-phosphate backbone are deprotonated.
D
DNA is electrically neutral overall because the charges of bases and sugars cancel exactly.
Verified step by step guidance1
Recall that DNA is a polymer made up of nucleotides, each consisting of a sugar (deoxyribose), a phosphate group, and a nitrogenous base.
Understand that the overall charge of DNA at physiological pH depends on the ionization state of its chemical groups, especially those that can gain or lose protons (H+ ions).
Identify which part of the nucleotide carries a charge: the phosphate group in the sugar-phosphate backbone has acidic properties and tends to lose protons, becoming negatively charged at physiological pH.
Recognize that the nitrogenous bases and sugars do not contribute significantly to the overall charge because they are mostly neutral or do not ionize under physiological conditions.
Conclude that the net negative charge of DNA arises primarily from the deprotonated phosphate groups in the backbone, making DNA negatively charged overall at physiological pH.
Related Videos
Related Practice
