#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: 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: 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: 1521
#Unit 4. Cell Communication and Cell Signaling
we examine how the deregulation of growth-promoting and growth-inhibiting signaling pathways contributes to tumorigenesis. Mutations-
A. A mutation that alters a single amino acid (valine to glutamine) in the transmembrane region of the HER2 receptor
B. A deletion that causes loss of the extracellular ligand-binding domain in the EGF receptor Results-
i. dimerization of the receptor, even in the absence of the normal EGF-related ligand, transforming it into the oncoprotein, a constitutively active kinase
ii. to constitutive activation of the kinase activity of the resulting oncoprotein
iii. no dimerization, even in the presence of the normal EGF-related ligand, repression of kinase activity
which of the following results are displayed after these mutations?
#Question id: 1522
#Unit 4. Cell Communication and Cell Signaling
Conversion of a proto-oncogene into an oncogene, also called activation, generally involves a gain-of-function mutation. Following statements are regarding to the mechanisms that produce oncogenes from the corresponding proto-oncogenes.
A. A change in a single base pair in a proto-oncogene that results in a hyperactive or constitutively active protein product.
B. A chromosomal translocation that fuses two genes together to produce a hybrid gene encoding a chimeric protein whose activity, unlike that of the parent proteins, is permanently suppress.
C. A chromosomal translocation that brings a growth regulatory gene under the control of alternative enhancers that cause inappropriate expression of the gene.
D. Amplification of a DNA segment including a proto-oncogene so that numerous copies exist, leading to overproduction of the encoded protein.
Which of the following statements are correct?
#Question id: 1523
#Unit 4. Cell Communication and Cell Signaling
Following statements are regarding to the apoptosis which is induced by trophic factors.
A. The presence of specific trophic factors (e.g., NGF) leads to activation of their cognate receptor tyrosine kinases (e.g., TrkA) and activation of the PKB pathway.
B. DNA damage or ultraviolet irradiation leads to induction of synthesis of the BH3-only Puma protein. Puma binds to Bak and Bax as well as to Bcl-2, allowing Bak and Bax to form oligomeric pores.
C. Removal of a cell from its substratum disrupts integrin signaling, leading to release of the BH3-only Bim protein from the cytoskeleton.
D. Binding of extracellular death signals, such as tumor necrosis factor and Fas ligand, to their receptors oligomerizes an associated protein (FADD), which in turn triggers the caspase cascade, leading to cell murder by apoptosis.
Which of the following pathway does not belong to the trophic factor inducing apoptotic pathway?