Once bound to Pol II, Ptefb phosphorylates the serine residue at position 2 of the CTD repeats. That phosphorylation event correlates with elongation. In addition, P-TEFb phosphorylates and thereby activates another protein, called SPT5, itself an elongation factor. Finally, TAT-SF1, yet another elongation factor, is recruited by P-TEFb. Thus, P-TEFb stimulates elongation in three separate ways.

TLS Online TPP Program

#Id: 1711

#Unit 4. Cell Communication and Cell Signaling

Healthy individuals generate IgE antibodies only in response to parasitic infections.

TLS Online TPP Program

#Id: 6023

#Unit 3. Fundamental Processes

DNA Pol a/ primase and DNA Pol d (which primarily act on the lagging strand) are only recruited after DNA unwinding.

TLS Online TPP Program

#Id: 5634

#Unit 7. System Physiology – Animal

Rods 

Have low acuity or resolution

are sensitive to low-intensity light

receptors for night vision (scotopic vision)

TLS Online TPP Program

#Id: 5324

#Unit 7. System Physiology – Animal

Isovolumetric Ventricular Relaxation

Closure of aortic valve producing the second heart sound (S2).

TLS Online TPP Program

#Id: 9788

#Unit 6. System Physiology – Plant

Mutations in the EDS1 (SA synthesis) (ENHANCED DISEASE SENSITIVITY 1) gene eliminate race‐specific resistance mediated by the TIR‐NB‐LRR class of R proteins