one of Antennapedia’s functions is to repress the genes that would trigger antenna and eye development.

TLS Online TPP Program

#Id: 6131

#Unit 3. Fundamental Processes

1-methyladenine and 3MC is corrected by an enzyme that uses an oxygenating mechanism alkB by reversal mechanism

TLS Online TPP Program

#Id: 6132

#Unit 3. Fundamental Processes

TLS Online TPP Program

#Id: 6133

#Unit 3. Fundamental Processes

The oxoG adduct is highly mutagenic because it can base-pair with adenine as well as with cytosine. If it base-pairs with adenine during replication, it gives rise to a G:C to T:A transversion, which is one of the most common mutations found in human cancers.

TLS Online TPP Program

#Id: 6134

#Unit 3. Fundamental Processes

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

TLS Online TPP Program

#Id: 6135

#Unit 3. Fundamental Processes

XPC= UvrA

XPA and XPD = UvrB, RPA

ERCC1-XPF, XPG = UvrC

TLS Online TPP Program

#Id: 6136

#Unit 3. Fundamental Processes

XPC detect distortions = UvrA in E. coli

Formation of the bubble involves the helicase activities of the proteins XPA and XPD (the equivalent to UvrB in E. coli) and the single-strand-binding protein RPA. The bubble creates cleavage sites 5’ to the lesion for a nuclease known as ERCC1-XPF and 3’ to the lesion for nuclease XPG (representing the function of UvrC). In higher cells, the resulting DNA strand is 24–32 nucleotides long. As in bacteria, the DNA strand is released to create a gap that is filled in by the action of DNA polymerase and ligase.

XPB and XPD are both helicases; the XPB helicase is required for promoter melting during transcription, while the XPD helicase performs the unwinding function in NER