Acyl-homomserine lactones (AHLs) are auto-inducers used by Gram-negative bacteria to communicate. Which statements are about that Quorum sensing signaling in bacteria. 

a. transcription is activated at low cell density

b. transcription is not activated at low cell density

c. transcription is activated at high cell density

d. transcription is not activated at high cell density

e. Upon reaching a threshold concentration, AHL can bind to its receptor LuxR.

f. Upon reaching a threshold concentration, AHL can bind to Lux box.

#Question id: 2947

#Unit 2. Cellular Organization

You perform an experiment where you prevent Cdc20 from binding to APC  in a cell line that usually completes the cell cycle in 60 minutes. Your experiment prevents Cdc20 from binding to APC for 120 minutes, and then you fix and stain the DNA, securin, separase and cohesin proteins. Which of the following would NOT be found in the observed cell?

#Question id: 12534

#Unit 10. Ecological Principles

#Question id: 4508

#Unit 3. Fundamental Processes

Statement: In the case of group II introns, the chemistry of splicing and the RNA intermediates produced are the same as those for nuclear pre-mRNA.

 Explanations: I. The intron uses an A residue within the branch site to attack the phosphodiester bond at the boundary between its 5’ end and the end of the 5’ exon-that is, at the 5’ splice site. This reaction produces the branched lariat.

II. A second reaction in which the newly freed 3’ -OH of the exon attacks the 3’splice site, releasing the intron as a lariat and fusing the 3’ and 5’ exons.

#Question id: 1363

#Unit 4. Cell Communication and Cell Signaling

Which of the following statements best describes the difference between low-affinity integrins and high-affinity integrins?

#Question id: 28844

#Unit 2. Cellular Organization

Which of the following is a key modulator of tau proteins?