ORC was first found in S. cerevisiae (where it may be called scORC),but similar complexes have now been characterized in Schizosaccharomyces pombe (spORC), Drosophila (DmORC ), and Xenopus (XIORC).

TLS Online TPP Program

#Id: 3335

#Unit 3. Fundamental Processes

Seven genes have been identified in which mutations give rise to XP, these genes specify proteins (such as XPA, XPC, XPD, XPF, and XPG;)

TLS Online TPP Program

#Id: 3337

#Unit 3. Fundamental Processes

In addition to proteins involved in NER, a variant form of XP called XP-V is caused by a defect in the translesion DNA polymerase, Pol h. The gene encoding Pol h is sometimes called XPV. Individuals with XP-V have a milder form of XP.

TLS Online TPP Program

#Id: 3339

#Unit 3. Fundamental Processes

Cells possessing a mutant Pol h are hindered in their ability to bypass thymine dimers during replication and must resort to using another translesion polymerase for bypass to avoid a block in replication. 

TLS Online TPP Program

#Id: 3346

#Unit 3. Fundamental Processes

Pol h (but not other translesion polymerases) correctly inserts As across from a thymine dimer, the use of other translesion polymerases may increase the frequency of mutagenesis

TLS Online TPP Program

#Id: 3348

#Unit 3. Fundamental Processes

Direct repair of alkylated bases by AlkB

TLS Online TPP Program

#Id: 3349

#Unit 3. Fundamental Processes

The AlkB protein is an alpa-ketoglutarate-Fe2+ dependent hydroxylase. It catalyzes the oxidative demethylation of 1-methyladenine and 3-methylcytosine residues