A. When a DNA molecule is negatively supercoiled, it is underwound. 

B. Any structural change involving DNA strand separation becomes more likely in negatively supercoiled DNA. 

C. Negative supercoiling makes establishment of left-handed Z-DNA in a segment of DNA 

D. The formation of plectonemic or solenoidal supercoils is favored as a means of negative supercoiling.

Find true and false

#Question id: 1240

#Unit 4. Cell Communication and Cell Signaling

Pull-down assays using proteins that ONLY bind to the GTP-bound version of the small G-protein can be used to detect when small G proteins like Rac1 have been activated by various growth factors.  You were given two lysates, one having been treated with platelet-derived growth factor (PDGF) and the other not treated with PDGF. This method is similar to performing co-IPs, so based on that knowledge, which of the following steps is erroneous?

#Question id: 1241

#Unit 4. Cell Communication and Cell Signaling

Which of the following is a common step in the opening/closing of ion channels by acetylcholine and rhodopsin binding to their receptors?

#Question id: 1242

#Unit 4. Cell Communication and Cell Signaling

Rhodopsin, a light-sensitive GPCR whose role in vision is dependent on its phosphorylation status, is influenced in part by the protein arrestin.  Which of the following is TRUE with regard to rhodopsin and vision?

#Question id: 1243

#Unit 4. Cell Communication and Cell Signaling

One form of receptor desensitization can be mediated by negative feedback involving phosphorylation of the receptor itself by a kinase activated downstream of a second messenger. The phosphorylated receptor likely:

#Question id: 1244

#Unit 4. Cell Communication and Cell Signaling

Which type of experimental evidence shows that the intrinsic GTPase activity of the Gα subunit is important for terminating effector activation?

#Question id: 1245

#Unit 4. Cell Communication and Cell Signaling

Many PTB-containing proteins act as docking sites for multiple proteins. If these proteins are involved in the RTK signal transduction pathway, they most likely: