What must first happen to DNA before it can be replicated?

What must first happen to DNA before it can be replicated?

• A. Unzipped
• B. Unwound
• C. Coiled
• D. Twisted

Answer: (A)

DNA replication starts when the two strands of the double helix are opened so each strand can serve as a template. This opening is best described as unzipping the DNA, where the hydrogen bonds between base pairs are broken to separate the strands. Helicase carries out this unzipping, creating the replication forks, while other proteins stabilize the single strands and relieve tension ahead of the fork. Only after the strands are unzipped can primase lay down RNA primers and DNA polymerase begin synthesizing the new complementary strands. So, the first essential step is unzipping the DNA to expose the single-stranded templates.

DNA replication starts when the two strands of the double helix are opened so each strand can serve as a template. This opening is best described as unzipping the DNA, where the hydrogen bonds between base pairs are broken to separate the strands. Helicase carries out this unzipping, creating the replication forks, while other proteins stabilize the single strands and relieve tension ahead of the fork. Only after the strands are unzipped can primase lay down RNA primers and DNA polymerase begin synthesizing the new complementary strands. So, the first essential step is unzipping the DNA to expose the single-stranded templates.