The Dictyostelia social amoebas are found in a wide range of soil habitats. They can come together to form a fruiting structure, in which a proportion of cells are sacrificed to build the stalk and the remainder differentiate into resilient dormant spores. This multicellular life cycle is common to all Dictyostelids. It consists of an interconnected programme of cell movement and cell differentiation, and has been intensively studied in the model organism D. discoideum. Few mutants (Column A) and phenotypes (Column B) are listed in the table given below.

Column A	Column B
A. Loss of function of cAMP-dependent protein kinase (PKA)	i. cell develop normally but unable to germinate
B. Loss of function of RegA	ii. Loose aggregate form
C. Loss of function of adenylate cyclase B	iii. No aggregation
D. Loss of function of gp80	iv. accumulation of cAMP and PKA activation

 Match the correct mutant with the observed phenotype.

#Question id: 13159

#Unit 4. Cell Communication and Cell Signaling

#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: 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: 1260

#Unit 4. Cell Communication and Cell Signaling

Which of the following statement regarding RTK/Ras pathway 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: 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?