DNA Replication in Eukaryotes

These flashcards cover key concepts and mechanisms involved in DNA replication in eukaryotes as presented in the lecture.

What initiates DNA replication in eukaryotes?

DNA replication begins at multiple sites on chromosomes called origins of replication.

What is the function of the Origin Recognition Complex (ORC)?

The ORC binds to autonomously replicating sequences (ARS) to mark the site for initiation of replication.

During which phase is the pre-replicative complex (pre-RC) assembled?

The pre-replicative complex is assembled during the G1 phase of the cell cycle.

What is the role of Cdc6 and Cdt1 in the assembly of the pre-RC?

Cdc6 and Cdt1 are licensing factors that help recruit MCM proteins to the origins of replication.

What must happen to origins of replication after S phase?

Origins must be de-licensed to prevent re-replication, which is accomplished by the MCM complex.

How do cyclin-dependent kinases (CDKs) function in DNA replication?

CDKs promote the transition of pre-RCs into active initiation complexes and control the timing of DNA replication origins firing.

Which polymerase is primarily responsible for synthesizing new DNA strands?

DNA Polymerase delta (Pol-δ) is primarily responsible for synthesizing new DNA.

What mechanism prevents re-replication of DNA?

Geminin prevents the assembly of new MCM proteins on DNA to ensure that replication occurs only once per cell cycle.

What are Okazaki fragments?

Okazaki fragments are short DNA segments synthesized discontinuously on the lagging strand during DNA replication.

Why are multiple origins of replication important?

Multiple origins ensure timely and efficient replication of the entire genome within the S phase time-frame.

What is the role of topoisomerases in DNA replication?

Topoisomerases relieve torsional stress and untangle DNA strands by creating reversible cuts.

What happens to Cdc6 and Cdt1 after the initiation of DNA replication?

Cdc6 and Cdt1 are released from the complex after initiation by ATP hydrolysis.

How does PCNA contribute to the process of DNA replication?

PCNA acts as a sliding clamp to enhance the processivity of DNA polymerase during DNA synthesis.

What is the significance of phosphorylation events in DNA replication?

Phosphorylation events regulate initiation, progression, and prevent re-initiation of DNA replication during the cell cycle.

How are RNA primers used in DNA replication?

RNA primers are synthesized by DNA polymerase alpha to provide a starting point for DNA synthesis.