In the salt fractionation most polar will be fractionated with large amount of salt.

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#Id: 5043

#Unit 3. Fundamental Processes

Dam (Dam-) mutants accumulates hemimethylated products after replication.

If the plasmid is methylated, it undergoes a single round of replication, and then the hemimethylated products accumulate.

Suggesting that a hemimethylated origin cannot be used to initiate a replication cycle.

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#Unit 3. Fundamental Processes

Only fully methylated origins can initiate replication;

hemimethylated daughter origins cannot be used again until they have been restored to the fully methylated state.

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#Id: 5045

#Unit 3. Fundamental Processes

The GATC sites AT THE ORIGIN remain hemimethylated for 13 minutes after replication called as refractory period of replication cycle or delay time.

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#Id: 5046

#Unit 3. Fundamental Processes

At typical GATC sites elsewhere in the genome, remethylation begins immediately (1.5 minutes) following replication.

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#Unit 3. Fundamental Processes

One other region behaves like oriC:

The promoter of the dnaA gene also shows a delay before remethylation begins.

While it is hemimethylated, the dnaA promoter is repressed, which causes a reduction in the level of DnaA protein.

So Initiation of Replication (E.coli) takes place when GATC at origin is full methylated as well as promoter of DnaA gene. 

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#Id: 5048

#Unit 3. Fundamental Processes

An unmethylated CG site remains unmethylated after replication.