TLS Online TPP Program

#Id: 5904

#Unit 3. Fundamental Processes

A new model for the structure of the DNA Pol III complex proposes a three-polymerase core structure, with two Pol III catalytic cores responsible for synthesis of the lagging strand and one for the leading strand.

TLS Online TPP Program

#Id: 5905

#Unit 3. Fundamental Processes

Enzymes responsible for PTJ Helicase is hexameric and motor that melts the duplex and requires ATP hydrolysis—typically 1 ATP is hydrolyzed for each base pair that is unwound.

TLS Online TPP Program

#Id: 5906

#Unit 3. Fundamental Processes

Each DNA helicase moves along ssDNA in a defined direction. This property is referred to as the polarity of the DNA helicase. DNA helicases can have a polarity of either 5’->3’ or 3’->5’.

TLS Online TPP Program

#Id: 5907

#Unit 3. Fundamental Processes

In the case of a DNA helicase that functions on the lagging-strand template of the replication fork, the polarity is 5’->3’ to allow the DNA helicase to proceed toward the duplex region of the replication fork The PhiX system, named originally for phage X174, requires an initiation complex consisting of additional components, called the primosome. This system is used when damage causes the replication fork to collapse and it must be restarted.

TLS Online TPP Program

#Id: 5908

#Unit 3. Fundamental Processes

E. coli SSB is a tetramer of 74 kD that binds single-stranded DNA cooperatively

TLS Online TPP Program

#Id: 5909

#Unit 3. Fundamental Processes

A common feature of all DNA polymerases is that they cannot initiate synthesis of a chain of DNA de novo, but can only elongate a chain.