Actin polymerization in vitro proceeds in three steps:

1.Nucleation phase

2.Elongation phase

3.Steady-state

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

TLS Online TPP Program

#Id: 9217

#Unit 6. System Physiology – Plant

Rubisco catalyzes oxygenation of ribulose 1,5-bisphosphate called C2 cycle

TLS Online TPP Program

#Id: 7410

#Unit 5. Developmental Biology

Once wingless and engrailed expression patterns are established in adjacent cells, this pattern must be maintained to retain the parasegmental periodicity of the body plan.

TLS Online TPP Program

#Id: 790

#Unit 3. Fundamental Processes

Sequences of Rho dependent transcription termination

1. Rho binds a rut site. 

2. The rho factor then tracks along the RNA until it catches up to RNA polymerase. 

3. When the RNA polymerase reaches the termination site, rho first freezes the structure of the polymerase and then invades the exit channel to destabilize the enzyme, causing it to release the RNA. 

4. Pausing by the polymerase at the site of termination allows time for rho factor to translocate to the hybrid stretch.

TLS Online TPP Program

#Id: 7363

#Unit 5. Developmental Biology

On the right side of the embryo, activin is expressed, along with activin receptor IIa. This activates Fgf8, a protein that blocks expression of the gene for Cerberus.