Most common CFTR mutation is a ΔF508 -

Prevents normal transport of CFTR to the plasma membrane by blocking its packaging into COPII vesicles budding from the ER. 

Change the conformation of the cytosolic portion of CFTR so that the signal is unable to bind to Sec24.

TLS Online TPP Program

#Id: 5040

#Unit 3. Fundamental Processes

The single replicator 245 bp required for E. coli chromosomal replication is called oriC. Two repeated motifs are critical for oriC function.

The 9-mer motif is the binding site for the E. coli initiator, DnaA, and is repeated five times at oriC.

The 13-mer motif, repeated three times, is the initial site of ssDNA formation during initiation.

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#Id: 5041

#Unit 3. Fundamental Processes

oriC also contains 11 GATC/CTAG repeats that are methylated on adenine on both strands.

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#Id: 5042

#Unit 3. Fundamental Processes

Before replication, the palindromic target GATC site is methylated by dam methylase on the N6 of A of each strand.

Replication generates hemimethylated DNA, in which one strand is methylated and one strand is unmethylated.

Thus, the replication event converts Dam target sites from fully methylated to hemimethylated condition.

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#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.

TLS Online TPP Program

#Id: 5044

#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.

TLS Online TPP Program

#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.