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Welcome to Molecular Biology MCQ-11 (CSIR NET Molecular Biology Questions). This MCQ set consists of Advanced (Post Graduate Level) Molecular Biology Multiple Choice Questions with Answer Key. All these questions were taken from the previous year question papers of CSIR JRF NET Life Sciences Examination. These questions can be used for the preparation of Competitive examinations in Biology / Life Sciences such as CSIR JRF NET, ICMR JRF, DBT BET JRF, GATE and other University Ph.D Entrance Examinations. After marking your answers, please click ‘SUBMIT‘ button to see your ‘SCORE‘ and ‘CORRECT ANSWERS‘.
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(1). The mismatch repair activity of E.coli repairs misincorporated bases which are not removed by the proofreading activity of DNA polymerase. However, while doing so, it has to decide which strand of the DNA is newly synthesized and which one is parental. Mismatch repair system does it by which one of the following ways? (CSIR_2015_II)
(a). It recognizes nearby GATC sequence.
(b). It recognizes any nearby palindromic sequence.
(c). It recognizes a specific repetitive sequence.
(d). It recognizes the hemi-methylated GATC sequence nearby.
(2). G-protein coupled receptors (GPCR) consist of three protein subunits α, β and γ. In unstimulated state, α subunit is GDP bound and GPCR is inactive. When GPCR gets activated, it acts like guanine nucleotide exchange (GEF) factor and induces α-subunit to release its bound GDP allowing GTP to bind in its place. In order to regulate G- protein activity by regulating GDP/GTP concentration, α subunit acts as: (CSIR_2015_II)
(a). GTPase
(b). GDP kinase
(c). cGMP-specific phosphodiesterase
(d). cAMP-specific phosphodiesterase
(3). Cellular level of tumour suppressor protein p53 is maintained by the ubiquitin ligase protein, Mdm2. Over expression of Mdm2 was found to convert a normal cell into cancer cells by destabilizing p53. Another protein p19ARF inhibits the activity of Mdm2 thus stabilizing p53. Loss of p19ARF function also converts normal cells into cancer cells. Based on the above information, which one of the following statements is correct? (CSIR_2015_II)
(a). Both MDM2 and p19ARF are oncogenes.
(b). Both MDM2 and p19ARF are tumour suppressor genes.
(c). MDM2 is an oncogene but p19ARF is a tumor suppressor gene.
(d). p19ARF is an oncogene but MDM2 is a tumor suppressor gene.
(4). Histone deacytalase (HDAC) catalyses the removal of acetyl group from N-terminal of histones. Which amino acid of histone is involved in this process? (CSIR_2016_I)
(a). Lysine
(b). Arginine
(c). Asparagine
(d). Histidine
(5). E.coli is being grown in a medium containing both glucose and lactose. On depletion of glucose, expression of -galactoside will: (CSIR_2016_I)
(a). Remain unchanged
(b). Increase
(c). Decrease
(d). Initially decrease and then increase
(6). Cyclins are regulatory subunits and cyclin dependent kinases (CDKs) are the catalytic subunits. Following diagram represents the involvement of cyclins and CDKs in various stages of cell cycle:
If we knock down cyclin D in a cell by shRNA, which one the following graphs correctly represents the level of CDK2 activity? (CSIR_2015_I)
(a). Graph 1
(b). Graph 2
(c). Graph 3
(d). Graph 4
(7). In a type of signal transduction pathway, ligand binding to a receptor triggers activation of a receptor-associated kinase. This kinase may be an intrinsic part of the receptor protein or tightly bound to the receptor. Receptors in which the tyrosine kinase is an intrinsic part of it’s polypeptide chain are called the receptor tyrosine kinase (RTK). Which one of the following statements regarding RTK is INCORRECT? (CSIR_2017_II)
(a). All RTKs have three essential components: an extracellular domain containing ligand binding site, a transmembrane domain and a cytoplasmic segment that includes a domain with protein tyrosine kinase activity.
(b). Most RTKs are monomeric and ligand binding to the extracellular domain induces formation of receptor dimers.
(c). All cytokine receptors belong to RTKs and cytokine binding activates tyrosine kinase and receptor dimerization.
(d). Ligand binding to RTK leads to autophosphorylation of the protein tyrosine kinase in the cytoplasmic domain. The activated kinase then phosphorylates several tyrosine residues in the receptor’s cytoplasmic domain.
(8). Two classes of genes – proto-oncogene and tumor suppressor gene usually contribute to the development of cancer. Following are some of the statements regarding both the genes.
(A). Proto-oncogenes result in the development of cancer by gain-offunction mutation whereas tumor suppressor gene leads to cancer development by loss-of-function mutation.
(B). Proto-oncogenes result in development of cancer by loss-of-function mutation whereas tumor suppressor gene leads to cancer development by gain-of-function mutation.
(C). Mutation in both the alleles of a protooncogene is required for induction of cancer whereas mutation in one of the two alleles in tumor suppressor gene is sufficient for promoting tumorigenesis.
(D). Mutation in one of the two alleles in proto-oncogene is sufficient for induction of cancer whereas mutation in both the alleles of a tumor suppressor gene is required for promoting tumorigenesis.
Which combinations of the above statements are true for both the genes? (CSIR_2017_II)
(a). A and B
(b). A and C
(c). A and D
(d). B and C
(9). Two important features which aid the development of a tumor and its metastasis are epithelial-to-mesenchymal transition and angiogenesis. A student tested four cell lines to determine their invasiveness and proliferation capability by checking the expression of VEGF-A, TWIST and Cyclin D1. Which one of the following figures is most likely to exhibit the characteristics of a highly metastatic cancer cell? (CSIR_2017_II)
(a). Graph 1
(b). Graph 2
(c). Graph 3
(d). Graph 4
(10). Several types of molecules including the transmembrane glycoproteins can function as matrix receptors and co-receptors. However, the principal receptors on animal cells for binding most extracellular matrix proteins are the integrins. Which of the following statements is NOT true for integrins? (CSIR_2017_II)
(a). Integrins are transmembrane linker proteins that link to the cytoskeleton.
(b). An integrin molelcule is composed of two non-covalently associated glycoprotein subunits α and β. Both subunits span the cell membrane, with short intracellular C-terminal tails and large N-terminal extracellular domains.
(c). The extracellular portion of the integrin dimer binds to specific carbohydrate residues in extracellular matrix proteins or to ligands on the surface of other cells.
(d). The intracellular portion binds to a complex of proteins that form a linkage to the cytoskeleton.
Answer Key
(1). Ans. (d). It recognizes the hemi-methylated GATC sequence nearby.
(2). Ans. (a). GTPase
(3). Ans. (c). MDM2 is an oncogene but p19ARF is a tumor suppressor gene.
(4). Ans. (a). Lysine
(5). Ans. (b). Increase
(6). Ans. (c). Graph 3
(7). Ans. (c). All cytokine receptors belong to RTKs and cytokine binding activates tyrosine kinase and receptor dimerization.
(8). Ans. (c). (A) and (D)
(9). Ans. (d). Graph 4
(10). Ans. (c). The extracellular portion of the integrin dimer binds to specific carbohydrate residues in extracellular matrix proteins or to ligands on the surface of other cells.