Question

When DNA replication begins, which of the following happens?

• A. The bond between the nitrogen base and sugar of each nucleotide breaks.
• B. The hydrogen bonds between the nucleotides forming a base pair break.
• C. The phosphodiester bonds between adjacent nucleotides break.
• D. DNA ligase unzips the double helix.

Answer 1

The correct option is B The hydrogen bonds between the nucleotides forming a base pair break.

At points where DNA synthesis has been initiated, the enzyme helicase (more specifically DNA helicase) uses energy to help unzip the double helix of the parental DNA by breaking the hydrogen bonds between the nucleotides of each base pair. It thus, forms the replication fork so that each of the two parental DNA strands (known as templates) could be copied from.