During DNA replication, the two strands separate as the _________ bonds connecting the parent strands are broken by an enzyme called ___________.

During DNA replication, the two strands separate as the _________ bonds connecting the parent strands are broken by an enzyme called ___________.

• A. Ionic bonds; helicase
• B. Covalent bonds; ligase
• C. Hydrogen bonds; helicase
• D. Peptide bonds; primase

Answer: (C)

Hydrogen bonds between complementary bases hold the two DNA strands together, and during replication those bonds are broken by the helicase enzyme to unwind and separate the strands. Helicase uses energy to disrupt these relatively weak bonds, creating the replication fork so each template strand can be copied. The backbone’s covalent phosphodiester bonds stay intact during this unwinding, which is why the option mentioning hydrogen bonds and helicase is the best fit. Other activities, like ligase sealing gaps or primase laying down primers, occur after the strands have been separated or involve different kinds of bonds, not the breaking of base-pair hydrogen bonds.

Hydrogen bonds between complementary bases hold the two DNA strands together, and during replication those bonds are broken by the helicase enzyme to unwind and separate the strands. Helicase uses energy to disrupt these relatively weak bonds, creating the replication fork so each template strand can be copied. The backbone’s covalent phosphodiester bonds stay intact during this unwinding, which is why the option mentioning hydrogen bonds and helicase is the best fit. Other activities, like ligase sealing gaps or primase laying down primers, occur after the strands have been separated or involve different kinds of bonds, not the breaking of base-pair hydrogen bonds.