DNA Replication
You can now identify the main components, explain the mechanism step by step, interpret an observation and distinguish related ideas.
Big idea
Each daughter DNA molecule contains one parental strand and one newly synthesized strand. Helicase separates the strands, creating templates whose exposed bases 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 pair with new nucleotides.
- DNA polymerase: DNA polymerase adds nucleotides to a growing 3-prime end using a template and 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: Labeled parental strands appear once in each daughter double helix.
2. Replication fork
Helicase separates the strands, creating templates whose exposed bases pair with new nucleotides.
Observation: A Y-shaped fork advances as hydrogen bonds between bases are disrupted.
3. DNA polymerase
DNA polymerase adds nucleotides to a growing 3-prime end using a template and primer.
Observation: New DNA is synthesized only in the 5-prime to 3-prime direction.