PIE-1 is placed into the P blastomeres through the action of the PAR-1 protein & it inhibit both SKN-1 and PAL-1 function in the P2 and subsequent germline cells.

TLS Online TPP Program

#Id: 3261

#Unit 3. Fundamental Processes

g-radiation and X-rays (ionizing radiation) are particularly hazardous because they cause double-strand breaks in the DNA, which are difficult to repair. If left unrepaired, double-strand breaks can be lethal to a cell.

TLS Online TPP Program

#Id: 3263

#Unit 3. Fundamental Processes

DNA is also subject to attack from reactive oxygen species (e.g., O2- , H2O2, and OH†). These potent oxidizing agents are generated by ionizing radiation and by chemical agents that generate free radicals. Oxidation of guanine, for example, generates 7,8-dihydro-8-oxoguanine, or oxoG. 

TLS Online TPP Program

#Id: 3264

#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 inhuman cancers.

TLS Online TPP Program

#Id: 3266

#Unit 3. Fundamental Processes

The carcinogenic effects of ionizing radiation and oxidizing agents are partly caused by free radicals that convert guanine to oxoG.

TLS Online TPP Program

#Id: 3267

#Unit 3. Fundamental Processes

Bruce Ames of the University of California at Berkeley devised a simple test for the potential carcinogenic effects of chemicals based on their capacity to cause mutations in the bacterium Salmonella typhimurium.

TLS Online TPP Program

#Id: 3268

#Unit 3. Fundamental Processes

The Ames test uses a strain of S. typhimurium that is mutant for the operon responsible for the biosynthesis of the amino acid histidine. For example, the mutant operon might contain a missense or a frameshift mutation in one of the genes for histidine biosynthesis.