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TLS Online TPP Program

#Question id: 2904

When the temperature of a solution of DNA is raised to near the boiling point of water, the optical density, (called absorbance) at 260 nm markedly increases, a phenomenon known as hyperchromicity. Which of the following properties gets changed due to subsequent denaturation of the DNA molecule?

#Unit 2. Cellular Organization

  1. The solutions of native DNA exhibit high viscosity because of the relatively rigid double helical, long and rod like character of DNA molecule. Denaturation causes a marked decrease in viscosity.

  2. Denaturation of DNA double helix can also be brought about by certain chemical agents such as urea and formamide. These chemical reagents enhance the aqueous solubility of the purine and pyrimidine groups.

  3. Double-stranded DNA shows a strong positive rotation which highly decreases with denaturation. This change is analogous to the change in rotation observed when the proteins are denatured.

  4. All of the above

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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-
TLS Online TPP Program

#Question id: 20336

#Unit 12. Applied Biology

Granule bound starch synthase I (GBSS l) is the main enzyme of amylose biosynthesis. Therefore ___________ activity of GBSS I is expected to increase the amylose content of starch