Multiple Choice
Which statement best describes the structure of a DNA molecule?
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7. DNA and Chromosome Structure
DNA Structure
Multiple Choice
In the structure of DNA, which component is primarily responsible for the molecule's overall negative charge at physiological pH?
A
The phosphate groups in the sugar-phosphate backbone
B
The deoxyribose sugars in the backbone
C
Hydrogen bonds between complementary base pairs
D
The nitrogenous bases (A, T, G, C)
Verified step by step guidance1
Understand the structure of DNA, which consists of a sugar-phosphate backbone and nitrogenous bases (adenine, thymine, guanine, and cytosine) paired via hydrogen bonds.
Recall that the sugar-phosphate backbone is made up of alternating deoxyribose sugars and phosphate groups.
Recognize that the phosphate groups contain negatively charged phosphate ions (PO4^{3-}) at physiological pH, contributing to the overall negative charge of DNA.
Note that the deoxyribose sugars are neutral molecules and do not contribute to the charge.
Understand that hydrogen bonds between base pairs and the nitrogenous bases themselves are not charged and therefore do not contribute to the overall negative charge of the DNA molecule.
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