In contrast to most alkylating agents, the hydroxylating agent hydroxylamine (NH2OH) has a specific mutagenic effect. It induces only G:C → A:T transitions.

TLS Online TPP Program

#Id: 3285

#Unit 3. Fundamental Processes

Eukaryotic cells also repair mismatches and do so using homologs to MutS (called MSH proteins for “MutS homologs”) and MutL (called MLH and PMS

TLS Online TPP Program

#Id: 3286

#Unit 3. Fundamental Processes

In BER, A DNA glycosylase recognizes a damaged base (in this case, a uracil) and cleaves between the base and deoxyribose in the backbone.

TLS Online TPP Program

#Id: 3289

#Unit 3. Fundamental Processes

n BER,  An AP endonuclease cleaves the phosphodiester backbone near the AP site

TLS Online TPP Program

#Id: 3290

#Unit 3. Fundamental Processes

In BER,  DNA polymerase I initiates repair synthesis from the free 3’ hydroxyl at the nick, removing (with its 5’-3’ exonuclease activity) and replacing a portion of the damaged strand. 

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.