According to the Switching mechanism, monomeric G proteins exist in two states. Match the following states (Column I) with correct mechanism (Column II).

Column I	Column II
A. “ON” state	i. switch I and switch II, are bound to the terminal γ phosphate of GTP through interactions with the backbone amide groups of conserved threonine and glycine residues.
B. “OFF” state	ii. GTPase-activating proteins
	iii. guanine nucleotide exchange factor
	iv. Due to the removal of the γ phosphate by GTPase-catalyzed hydrolysis causes switch I and switch II to relax into a different conformation

#Question id: 1520

#Unit 4. Cell Communication and Cell Signaling

Following statements are regarding to enzymatic processing of benzo(a)pyrene to a more potent mutagen and carcinogen.

A. Liver enzymes, particularly P-450 enzymes, modify benzo(a)pyrene in a series of reactions, producing 7,8-diol-9,10-epoxide, a highly potent mutagenic species that reacts with DNA primarily at the N2 atom of a guanine base.

B. The adduct, (+)-trans-anti-B(a)P-N2-dG, causes polymerase to insert an A rather than a C opposite the modified G base. Next time the DNA is replicated, a T will be inserted opposite the A, and the mutation will be complete.

C. Potent mutagen majorly causes conversion of guanine (G) to thymine (T) bases, a transition mutation.

D. When this potent mutagen applied to cultured bronchial epithelial cells, activated benzo(a)pyrene induces many mutations, including activating mutations at codons 175, 248, and 273 of the p53 gene.

Which of the following statements are correct?

#Question id: 1519

#Unit 4. Cell Communication and Cell Signaling

Following statements are regarding to the FOXO3a protein.

A. In the presence of growth factors, FOXO3a is non phosphorylated and mainly localizes to the nucleus, where it activates transcription of several genes encoding pro-apoptotic proteins.

B. When growth factors are removed from the cells, PKB becomes active and phosphorylates FOXO3a.

C. Phosphorylated FOXO3a binds to cytosolic phosphoserine-binding protein 14-3-3 to bind FOXO3a and thus sequester it in the cytosol.

D. Dephosphorylated FOXO3a binds to cytosolic phosphoserine-binding protein 14-3-3 to bind FOXO3a and thus sequester it in the cytosol.

Which of the following is correct?

#Question id: 1518

#Unit 4. Cell Communication and Cell Signaling

Following statements are regarding to the some cancers harbor characteristic chromosome alterations. Chronic myelogenous leukemia (CML), a common leukemia in humans, was found to be associated with the Philadelphia chromosome.

A. Philadelphia chromosome is generated by a translocation between chromosomes 22 and 9. The two chromosomes exchange their terminal regions, which leads to a characteristic alteration in the size of chromosome 9.

B. At the breakpoint of this translocation, a new fusion protein, the BCR-ABL fusion, is generated.

C. The BCR-ABL fusion protein is a constitutively active kinase that phosphorylates multiple signal-transducing proteins.

D. If this translocation occurs in a hematopoietic cell in the bone marrow, the activity of the chimeric BCR-ABL oncogene dephosphorylate proteins thereby activating many intracellular signal-transducing proteins.

Which of the following statements are 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.

#Question id: 1264

#Unit 4. Cell Communication and Cell Signaling

 Desmosomes

#Question id: 1265

#Unit 4. Cell Communication and Cell Signaling

An example of an integrin containing cell junction is