Multiple Choice
In the structure of DNA, what five-carbon sugar is found in the backbone of each nucleotide?
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7. DNA and Chromosome Structure
DNA Structure
Multiple Choice
In the DNA double helix, what holds the two antiparallel strands together?
A
Covalent disulfide bridges between paired bases
B
Hydrogen bonds between complementary nitrogenous bases (A–T and G–C)
C
Hydrophobic interactions between the sugar-phosphate backbones of the two strands
D
Phosphodiester bonds between nucleotides on opposite strands
Verified step by step guidance1
Recall the structure of DNA, which consists of two antiparallel strands forming a double helix.
Understand that each strand has a sugar-phosphate backbone connected by covalent phosphodiester bonds, but these bonds are within a single strand, not between strands.
Identify that the two strands are held together by interactions between nitrogenous bases from each strand, which pair specifically (A with T, and G with C).
Recognize that these base pairs are connected by hydrogen bonds, which are weaker than covalent bonds but strong enough to stabilize the double helix while allowing strand separation during replication.
Conclude that the correct interaction holding the two strands together is hydrogen bonding between complementary nitrogenous bases, not covalent disulfide bridges, hydrophobic interactions between backbones, or phosphodiester bonds between strands.
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