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TLS Online TPP Program

#Question id: 7160

How does the dose-dependence of retinoic acid treatment support the notion that a gradient of retinoic acid can act as a morphogen along the proximo-distal axis in the limb?

#Unit 5. Developmental Biology
  1. Treatment with high levels of retinoic acid causes a proximal blastema to be respecified as a distal blastema, and only distal structures are regenerated.
  2. Treatment with high levels of retinoic acid causes any blastema to form only distal structures.
  3. Treatment with high levels of retinoic acid causes any blastema to be respecified as a proximal blastema, but it will form only proximal structures.

  4. Treatment with high levels of retinoic acid causes a distal blastema to be respecified as a proximal blastema, and regeneration of a full limb may be initiated from proximal values.

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TLS Online TPP Program

#Question id: 20330

#Unit 4. Cell Communication and Cell Signaling

What does the LuxR gene do?
TLS Online TPP Program

#Question id: 20331

#Unit 4. Cell Communication and Cell Signaling

LuxR is analogous to certain eukaryotic regulatory proteins, such as
TLS Online TPP Program

#Question id: 20332

#Unit 4. Cell Communication and Cell Signaling

What is LuxR and LuxI?
TLS Online TPP Program

#Question id: 20333

#Unit 4. Cell Communication and Cell Signaling

Choose true statements about Ax21-mediated quorum sensing;
a. It is a highly conserved sulfated peptide secreted by Xanthomonas oryzae.
b. Ax21 is sulfated by RaxST, which is a putative tyrosine sulfotransferase.
c. Sulfated Ax21 is secreted via the RaxABC type I secretion system
d. Sulfated Ax21 secreted is recognized by the rice XA21 receptor.
TLS Online TPP Program

#Question id: 20334

#Unit 4. Cell Communication and Cell Signaling

Sulfotransferases are the first enzymes of the core sulfation pathways, they transfer sulfate from PAPS to the hydroxyl or amino group of a wide variety of acceptors, as given below
a. Molecular basis of symbiotic host specificity in Rhizobium meliloti: nodH and nodPQ genes encode the sulfation of lipochito-oligosaccharide signals
b. Sulfation of the choriogonadotropin alpha subunit in human placental explants
c. Tyrosine sulfation of the amino terminus of CCR5 facilitates HIV-1 entry
d. A tyrosine-sulfated peptide based on the N terminus of CCR5 interacts with a CD4-enhanced epitope of the HIV-1 gp120 envelope glycoprotein and inhibits HIV-1 entry.
e. The Xanthomonas oryzae pv. oryzae raxP and raxQ genes encode an ATP sulfurylase and APS kinase that are required for AvrXa21 avirulence.
Which one of the following combination of above statements is correct?
TLS Online TPP Program

#Question id: 20335

#Unit 4. Cell Communication and Cell Signaling

Quorum sensing-mediates the social cooperation and conflict both-