Biology / Unit 6: DNA and Protein Synthesis
6.2 DNA Replication
Notes
Before a cell divides, it copies its DNA in S phase. This is replication.
- The enzyme helicase unzips the double helix by breaking hydrogen bonds between bases.
- DNA polymerase adds new nucleotides that match each old strand using base pairing.
- Replication is semiconservative: each new DNA molecule has one old strand and one new strand.
- DNA polymerase also proofreads to fix most mistakes.
Practice
Which enzyme unzips the DNA double helix?
Helicase breaks the hydrogen bonds between base pairs.
Replication is called semiconservative because:
Each old strand serves as a template and stays in a new molecule.
When during the cell cycle is DNA replicated?
DNA must be copied before mitosis begins.
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