Campbell Biology Concepts & Connections Practice Test

Covalent bonds on DNA connect which components to form the backbone?

The nitrogen bases across strands The sugar to the base The sugar of one nucleotide to the phosphate of the next nucleotide The phosphate groups to the bases

Correct Answer:

The sugar of one nucleotide to the phosphate of the next nucleotide

Explanation:

DNA’s backbone is the sugar-phosphate chain. Covalent phosphodiester bonds connect the deoxyribose sugar of one nucleotide to the phosphate group of the next nucleotide, creating a continuous sugar–phosphate backbone along each strand. This backbone runs the length of the molecule, while the nitrogenous bases extend inward and pair with the opposite strand via hydrogen bonds. So the covalent link that forms the backbone is between the sugar of one nucleotide and the phosphate of the next.

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