In the absence of both activator and repressor, RNA polymerase occasionally binds the promoter spontaneously and initiates a low level (basal level) of transcription. 

TLS Online TPP Program

#Id: 6012

#Unit 3. Fundamental Processes

Cdc6 has an ATPase activity that is required for it to support initiation.

TLS Online TPP Program

#Id: 6013

#Unit 3. Fundamental Processes

The presence of Cdc6 and Cdt1 at the yeast origin allows the MCM proteins to bind to the complex in G1 in the inactive state.

TLS Online TPP Program

#Id: 6014

#Unit 3. Fundamental Processes

Helicases are loaded during G1 are only activated to unwind DNA and initiate replication after cells pass from the G1 to the S phase of the cell cycle in effect with S phase CDKC

TLS Online TPP Program

#Id: 6015

#Unit 3. Fundamental Processes

The origin enters S phase in the condition of a prereplication complex, which contains ORC, Cdc6, Cdt1, and the inactive helicase

TLS Online TPP Program

#Id: 6016

#Unit 3. Fundamental Processes

The MCM2-7 proteins form a six-member ring-shaped complex around DNA. MCM2,3,5 are regulatory, while MCM4,6,7 have the helicase activity.

TLS Online TPP Program

#Id: 6017

#Unit 3. Fundamental Processes

In mammalian cells, Cdt1 is targeted for degradation by the action of a protein complex that is recruited to the origin of replication by PCNA, the eukaryotic counterpart of the bacterial b clamp.