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: 9316

#Unit 4. Cell Communication and Cell Signaling

Light absorption by rhodopsin→activation of a cGMP PDE → hydrolyzes cGMP to 5′-GMP→ cGMP levels  drop →channel close →membrane hyperpolarization→reduction in NT release→transmitted to brain

TLS Online TPP Program

#Id: 8318

#Unit 2. Cellular Organization

Nucleation phase 

Two G-actin molecules bind relatively weakly to each other, but addition of a third actin monomer to form a trimer makes the entire group more stable, acts as a nucleus for polymerization.

TLS Online TPP Program

#Id: 3600

#Unit 3. Fundamental Processes

All the amino acids except methionine and tryptophan have more than one codon.

TLS Online TPP Program

#Id: 7390

#Unit 5. Developmental Biology

TLS Online TPP Program

#Id: 9936

#Unit 4. Cell Communication and Cell Signaling

Extracellular Bacteria