Multiple Choice
In the DNA double helix, what type of chemical bond holds the sugar-phosphate backbone together within a single strand?
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7. DNA and Chromosome Structure
DNA Structure
Multiple Choice
In the DNA double helix, what type of interaction primarily holds complementary nitrogenous bases together across the two strands?
A
Hydrogen bonds between complementary base pairs (A–T and G–C)
B
Ionic bonds between the sugar-phosphate backbones of the two strands
C
Phosphodiester bonds between bases on opposite strands
D
Covalent bonds formed directly between A and T and between G and C
Verified step by step guidance1
Recall the structure of the DNA double helix, which consists of two strands running in opposite directions, with nitrogenous bases paired in the center.
Identify the types of chemical bonds present in DNA: phosphodiester bonds link nucleotides within a single strand, while interactions between strands involve different types of bonds.
Understand that the sugar-phosphate backbone is held together by covalent phosphodiester bonds, but these do not connect the two strands to each other.
Focus on the interactions between complementary nitrogenous bases (A pairs with T, and G pairs with C) across the two strands, which are held together by hydrogen bonds.
Conclude that hydrogen bonds between complementary base pairs are the primary interactions stabilizing the two strands of the DNA double helix.
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