Translesion synthesis is catalyzed by a specialized class of DNA polymerases that synthesize DNA directly across the site of the damage. In E. coli, DNA Pol IV (DinB) or DNA Pol V (a complex of the proteins UmuC and UmuD’) performs translesion synthesis.  DinB and UmuC are members of a distinct family of DNA polymerases found in many organisms known as the Y family of DNA 

polymerases. There are five translesion polymerases known in humans, four of which belong to the Y family.

TLS Online TPP Program

#Id: 5022

#Unit 3. Fundamental Processes

Interphase = G1 + S + G2

The start of S phase is signaled by the activation of the first replicon, usually in euchromatin, in areas of active genes.

TLS Online TPP Program

#Id: 5023

#Unit 3. Fundamental Processes

Replication initiates at the bacterial origin when a cell passes a critical threshold of size/mass triggered by G1 phase protein synthesis. 

TLS Online TPP Program

#Id: 5024

#Unit 3. Fundamental Processes

DnaA protein, An initiator protein is synthesized continuously throughout the cell cycle; and its accumulation of a critical amount would trigger initiation.

TLS Online TPP Program

#Id: 5025

#Unit 3. Fundamental Processes

Bacteria have two links between replication and cell growth:

• The frequency of initiation of cycles of replication is adjusted to fit the rate at which the cell is growing. 

• The completion of a replication cycle is connected with division of the cell.

TLS Online TPP Program

#Id: 5026

#Unit 3. Fundamental Processes

The rate of bacterial growth is assessed by the doubling time, the period required for the number of cells to double.

The shorter the doubling time, the faster the bacteria are growing.

Escherichia coli growth rates can range from doubling times as fast as 18 minutes to slower than 180 minutes.

TLS Online TPP Program

#Id: 5027

#Unit 3. Fundamental Processes

The bacterial chromosome is a single replicon; thus, the frequency of replication cycles is controlled by the number of Initiation events at the single origin.