Which of the following statements is/are CORRECT from the following?

I. The chromosome of the small monkey DNA virus SV40 is a circular, double-helical DNA molecule of 5000 bp.

II. The phage Lambda genome is a linear single-stranded molecule in the virion particle.

III. Circular DNA molecules purified from both bacteria and eukaryotes are usually negatively supercoiled, having values of sigma of approximately –0.06.

IV. Prokaryotes have a special type I topoisomerase known as “DNA gyrase” that introduces, rather than removes, negative supercoils.

V. DNA disentanglement, generally catalyzed by a type II topoisomerase, is also required for a successful round of DNA replication and cell division in eukaryotes.

#Question id: 1258

#Unit 4. Cell Communication and Cell Signaling

Following statements are regarding to the desensitization mechanism of GPCR.

A. Several residues in the cytosolic domain of the β-adrenergic receptor are phosphorylated by the enzyme rhodopsin kinase.

B. β-Arrestin binds to specific phosphorylated tyrosine residues in the C-terminal segment of G protein–coupled receptors (GPCRs).

C. Clathrin and AP2, two other proteins bound by β-arrestin, promote endocytosis of the receptor.

D. β-Arrestin also functions in transducing signals from activated receptors by binding to and activating several cytosolic protein kinases like Src activates the MAP kinase pathway, leading to phosphorylation of key transcription factor.

Which of the following combination is incorrect?

#Question id: 1259

#Unit 4. Cell Communication and Cell Signaling

Following statements are regarding to the phosphoinositide pathway.

A. many activated RTKs and cytokine receptors initiate phosphoinositide pathway by recruiting the enzyme phosphatidylinositol-3 kinase (PI-3 kinase) to the membrane.

B. PI-3 kinase adds a phosphate to the 3′ carbon in one of two separate phosphatidylinositol substrates, leading to formation of two phosphatidylinositol 3-phosphates: PI(3,4)P2 or I(3,4,5)P3

C. PI-3 kinase pathway can trigger cell division and prevent apoptosis, thus ensuring cell survival by the activation of PKB.

D. Activated PKB phosphorylates FOXO3a, which induces the expression of several antiapoptotic genes.

Which of the following combination is correct?

#Question id: 1260

#Unit 4. Cell Communication and Cell Signaling

Which of the following statement regarding RTK/Ras pathway is incorrect?

#Question id: 1261

#Unit 4. Cell Communication and Cell Signaling

A FOXO3a mutant in which the three serine residues that are targets for PKB are mutated to alanine then what will be the result?

#Question id: 1262

#Unit 4. Cell Communication and Cell Signaling

Although MAP kinase is often activated in multicellular animals by RTKs or cytokine receptors, signaling from other receptors can activate MAP kinase in other eukaryotic cells. we consider the mating pathway in the yeast S. cerevisiae, a well-studied example of a MAP kinase cascade linked to G protein–coupled receptors (GPCRs). Which of the following statement is incorrect?

#Question id: 1263

#Unit 4. Cell Communication and Cell Signaling

The major classes of CAMs include

a. cadherins.    b. fibronectin.    c. Ig-superfamily CAMs.      d. P-selectins.