Chapter 8 b) DNA replication

What are the three possible mechanisms of DNA replication?

1. Semiconservative mechanism, 2. Conservative mechanism, 3. Dispersive mechanism.

What does the semi-conservative mechanism of DNA replication produce?

It produces DNA molecules with one parental strand and one newly made strand.

What was the key finding of the Meselson and Stahl Experiment?

DNA replication is semi-conservative.

Which enzyme is responsible for synthesizing new DNA strands during replication?

DNA polymerase.

In a semi-conservative replication, how do the new DNA strands relate to the original strands?

Each new DNA molecule contains one old strand and one new strand.

What role does DNA helicase play in DNA replication?

DNA helicase unwinds the DNA helix.

What is the function of DNA ligase?

DNA ligase seals the nicks left between adjacent bases after RNA primers are replaced with DNA.

What are Okazaki fragments?

Short DNA segments synthesized on the lagging strand during DNA replication.

How is the direction of nucleotide addition during DNA replication characterized?

Nucleotides are always added at the 3’-end of the new strand.

How many origins of replication do eukaryotes have compared to bacteria?

Eukaryotes require multiple origins, while bacteria have a single origin.

The 5’ to 3’ end of the new DNA strand is known as the….. Does it have continuous synthesis?

Leading strand. Yes, it is synthesized continuously.

The 3’ to 5’ is known as the….. Is synthesis continuous?

Lagging strand. No, it is synthesized discontinuously.

What are SSB’s and what are their role?

• Single-strand binding proteins (SSBs) are proteins that bind to the DNA strands during replication to prevent them from re-annealing

• Their primary role is to stabilize the unwound DNA strands, allowing for proper access by the replication machinery

What is topoisomerase and what’s its role?

Topoisomerase is an enzyme that alleviates torsional strain in DNA during replication. Its role is to introduce cuts in the DNA strands to relieve supercoiling, allowing the strands to unwind and progress through replication.

What is the role of primase?

Primase is an enzyme that synthesizes short RNA primers on the lagging strand, providing a starting point for DNA polymerase to begin DNA synthesis.

What’s the difference between DNA polymerase I and DNA polymerase III?

DNA polymerase I is primarily responsible for removing RNA primers and filling in the gaps with DNA, whereas DNA polymerase III is the main enzyme for elongating the new DNA strand during replication.

What does the sliding clamp do?

The sliding clamp is a protein complex that encircles the DNA strand, facilitating the processivity of DNA polymerase by holding it in place during elongation. This ensures that DNA synthesis occurs efficiently without frequent dissociation from the template.