DNA Replication
This lesson connects molecular mechanisms, cell behavior and biological evidence. Instead of memorizing isolated terms, follow what changes, what is measured, where the process occurs and why the outcome matters to a living system.
Big idea
Each daughter DNA molecule contains one parental strand and one newly synthesized strand. Helicase separates the strands, creating templates whose exposed bases can pair with new nucleotides.
Learning goals
- Semiconservative replication: Each daughter DNA molecule contains one parental strand and one newly synthesized strand.
- Replication fork: Helicase separates the strands, creating templates whose exposed bases can pair with new nucleotides.
- DNA polymerase: DNA polymerase adds nucleotides to a growing 3-prime end using a template and a primer.
- Leading and lagging strands: One strand is made continuously, while the other is made as Okazaki fragments that are joined.
- Proofreading and fidelity: Polymerase proofreading and repair systems correct most mismatches, making replication highly accurate.
Core concepts
1. Semiconservative replication
Each daughter DNA molecule contains one parental strand and one newly synthesized strand.
Observation or application: Labeled parental strands appear once in each daughter double helix.
2. Replication fork
Helicase separates the strands, creating templates whose exposed bases can pair with new nucleotides.
Observation or application: A Y-shaped fork advances as hydrogen bonds between bases are disrupted.