TLS Online TPP Program

#Question id: 15417


Sequence of amphibian lens induction postulated by experiments on embryos of the frog Xenopus laevis ; EXCEPT

#Unit 5. Developmental Biology
  1. Unidentified inducers (possibly from the foregut endoderm and cardiac mesoderm) cause the synthesis of the Otx2 transcription factor in the head ectoderm during the late neurula stage.
  2. As the neural folds rise, inducers from the anterior neural plate (including the region that will form the retina) induce Pax6 expression in the anterior ectoderm that can form lens tissue.
  3. As the neural folds rise, inducers from the anterior neural plate (including the region that will form the retina) induce Pax6 expression in the anterior ectoderm that can form lens tissue.
  4. The optic vesicle secretes BMP and FGF family paracrine factors, which induce the synthesis of the Sox transcription factors and initiate observable lens formation
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TLS Online TPP Program

#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?

TLS Online TPP Program

#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?

TLS Online TPP Program

#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?

TLS Online TPP Program

#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:

TLS Online TPP Program

#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?

TLS Online TPP Program

#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: