Multiple Choice
In DNA structure, what overall net charge does DNA carry at physiological pH, and what feature of the molecule is primarily responsible for this charge?
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7. DNA and Chromosome Structure
DNA Structure
Multiple Choice
In the structure of DNA, what does the backbone of the DNA double helix primarily consist of?
A
A continuous chain of amino acids linked by peptide bonds
B
Alternating deoxyribose sugars and phosphate groups linked by phosphodiester bonds
C
Ribose sugars and uracil-containing nucleotides typical of RNA
D
Alternating nitrogenous bases (A, T, G, C) paired by hydrogen bonds
Verified step by step guidance1
Recall the basic structure of DNA, which is composed of nucleotides. Each nucleotide consists of three parts: a phosphate group, a sugar molecule (deoxyribose in DNA), and a nitrogenous base (adenine, thymine, guanine, or cytosine).
Understand that the backbone of the DNA double helix is formed by the sugar and phosphate groups of the nucleotides. These components link together to create a continuous chain.
Recognize that the sugar and phosphate groups are connected by phosphodiester bonds, which are covalent bonds linking the 3' carbon atom of one sugar to the 5' carbon atom of the next sugar via a phosphate group.
Note that the nitrogenous bases (A, T, G, C) are not part of the backbone but instead project inward from the sugar-phosphate backbone and pair with complementary bases on the opposite strand through hydrogen bonds.
Conclude that the backbone of DNA is primarily made up of alternating deoxyribose sugars and phosphate groups linked by phosphodiester bonds, which provides structural stability to the DNA molecule.
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