All proteins found in the nucleus, histones, transcription factors,  DNA & RNA polymerases are synthesized in the cytoplasm and imported into the nucleus through nuclear pore complexes.

TLS Online TPP Program

#Id: 3291

#Unit 3. Fundamental Processes

In BER, The nick remaining after DNA polymerase I has dissociated is sealed by DNA ligase.

TLS Online TPP Program

#Id: 3293

#Unit 3. Fundamental Processes

Base excision repair of a T∙G mismatch. 

TLS Online TPP Program

#Id: 3297

#Unit 3. Fundamental Processes

oxoG:A repair, Oxidation of guanine produces oxoG. 

The modified base can be repaired before replication by DNA glycosylase via the base excision pathway. 

If replication occurs before the oxoG is removed, resulting in the misincorporation of an A, then a fail-safe glycosylase can remove the A, allowing it to be replaced by a C. 

This provides a second opportunity for the DNA glycosylase to remove the modified base.

TLS Online TPP Program

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#Unit 3. Fundamental Processes

Another example of a fail-safe system is a glycosylase that removes a T opposite a G. Such a T:G mismatch can arise, as we have seen, by spontaneous deamination of 5-methylcytosine,which occurs frequently in the DNA of vertebrates. 

TLS Online TPP Program

#Id: 3301

#Unit 3. Fundamental Processes

DNA lesions that cause large distortions in the helical structure of DNA generally are repaired by the nucleotide-excision system, a repair pathway critical to the survival of all free-living organisms. 

TLS Online TPP Program

#Id: 3303

#Unit 3. Fundamental Processes

Nucleotide excision repair in E. coli is largely accomplished by four proteins: UvrA, UvrB, UvrC, and UvrD