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Welcome to Molecular Biology MCQ-12 (Molecular Biology Questions for CSIR NET). 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). Each aminoacyl-tRNA synthetase is precisely able to match an amino acid with the tRNA containing the correct corresponding anticodon. Most organisms have 20 different tRNA synthetases, however some bacteria lack the synthetase for charging the tRNA for glutamine (tRNAGln) with its cognate amino acid. How do these bacteria manage to incorporate glutamine in their proteins? Choose the correct answer. (CSIR_2016_I)
(a). Glutamine is not present in the newly synthesized bacterial protein. Post translational modification converts glutamate to glutamine at the required sites.
(b). In these bacteria, the aminoacyl tRNA synthetase specific for tRNA glutamate (tRNAglu) also charges tRNAgln with glutamine.
(c). In these bacteria, the aminoacyl tRNA synthetase specific for tRNAglu also charges tRNAgln with glutamate. A second enzyme then converts the glutamate of the charged tRNAgln to glutamine.
(d). In these bacteria, the aminoacyl tRNA synthetase charges tRNAglu with either glutamate or glutamine according to their requirement during protein synthesis.
(2). As topoisomerases play an important role during replication, a large number of anticancer drugs have been developed that inhibit the activity of these enzymes. Which of the following statements is NOT true about topoisomerases as a potential anticancer drug target? (CSIR_2016_I)
(a). As cancer cells are rapidly growing cells, they usually contain higher level of topoisomerases.
(b). The transient DNA breaks created by topoisomerases are usually converted to permanent breaks in the genome in the presence of topoisomerase targeted drugs.
(c). As cancer cells often have impaired DNA repair pathways, they are more susceptible towards topoisomerase targeted drugs.
(d). The drugs which specifically target topoisomerases, usually do not affect normal fast growing cells.
(3). Transposons can be primarily categorized into two types, DNA transposons and retrotrans-posons. Given below is some information regarding the above.
(A). Eukaryotic DNA transposons excise themselves from one place in the genome and integrate into another site.
(B). Retrotransposons are RNA sequences that are first reverse transcribed into cDNA and then integrate into the genome.
(C). Retrotransposons move by a copy and paste mechanism through an RNA intermediate.
(D). As DNA transposons move via a cut and paste mechanism, there can never be an increase in the copy number of a transposon.
Which of the statement(s) is/are true? (CSIR_2016_I)
(a). A and C
(b). B and D
(c). B only
(d). D only
(4). In a signalling event, binding of an extracellular ligand activates G-protein coupled receptor (GPCR) that eventually activates phospholipase C-β. Which one of the following statements truly reflects the function of phospholipase C-β ? (CSIR_2017_II)
(a). Phospholipase C-β converts PI (3,4,5)P3 to PI (4,5)P2
(b). Phospholipase C-β converts PI (4)P to PI (4,5)P2
(c). Phospholipase C-β converts PI (4,5)P2 to diacylglycerol and IP3
(d). Phospholipase C-β converts PI (5)P to PI (4,5)P2
(5). Select a cellular body which is NOT a part of the nuclear bodies: (CSIR_2017_II)
(a). P-bodies
(b). Nucleolus
(c). Cajal bodies
(d). Interchromatin granule clusters
(6). Which one of the following statements about chromatin is NOT true? (CSIR_2017_II)
(a). DNA winds approximately 1.65 times around the nucleosomes
(b). H2A-H2B bind to both the entry and exit ends of DNA in nucleosomes
(c). Covalent modification of histones influence chromatin compaction
(d). Non-histone proteins are part of mitotic chromosomes
(7). During eukaryotic cell division, metaphase to anaphase transition is regulated by degradation of (CSIR_2017_II)
(a). Cyclin B1
(b). CDK1
(c). Aurora A kinase
(d). Polo-like kinase
(8). A highly specific inhibitor that targets the phosphorylation activity of TFIIH is added to an in vitro transcription reaction. Which one of the following steps is most likely to be affected? (CSIR_2017_II)
(a). Binding of RNA polymerase to promoter sequence
(b). Promoter clearance
(c). Recruitment of TFIID
(d). Open promoter complex formation
(9). During eukaryotic protein synthesis, stress conditions result in activation of specific kinases leading to phosphorylation of a key translation initiation factor that inhibits protein synthesis from a large number of cellular mRNA. Which one of the following factors is the target of the kinase? (CSIR_2017_II)
(a). eIF4E
(b). eIF4G
(c). eIF2α
(d). Gcn4
(10). Proteins with cytoplasmic domains having tyrosine kinase activity do NOT act as receptors for (CSIR_2017_II)
(a). Epidermal growth factor (EGF)
(b). Platelet-derived growth factor (PDGF)
(c). Insulin
(d). Transferrin
(11). Which one of the following is a group of signalling molecules that act as morphogens during development of an organism and its effects are mediated through the receptor Patched and its binding partner Smoothened? (CSIR_2017_II)
(a). Hedgehog protein
(b). Notch protein
(c). Wnt protein
(d). β-catenin
(12). Junctions which tether cytoskeletal filaments inside the cell are known as
(a). anchoring junctions
(a). occluding junctions
(c). channel – forming junctions
(d). signal – relaying junctions
(13). Which one of the following statements about the nuclear receptor superfamily is NOT true? (CSIR_2015_II)
(a). The receptors are always cytosolic, where they remain associated with heat-shock proteins and have variable ligand binding domains in the N-terminal region.
(b). The receptors have characteristic repeat of the C4 zinc-finger motif
(c). The receptors are either homodimeric or heterodimeric, and in the absence of their hormone ligand, the heterodimeric receptors repress transcription, when bound to their response elements.
(d). The receptors have a unique N-terminal region of variable length and may contain a nuclear localization signal between the DNA- and ligand-binding domains.
(14). The genome of a bacterium is composed of a single DNA molecule which is 109 bp long. How many moles of genomic DNA is present in the bacterium? [Consider Avogadro No. 6 X 1023]. (CSIR_2015_II)
(a). 1/6 X 10-23
(b). 1/6 X 10-14
(c). 6 X 1014
(d). 6 X 1023
(15). The mutation in an oncogene falls under which of the following classes? (CSIR_2015_II)
(a). Loss of function mutation
(b). Frame shift mutation
(c). Gain of function mutation
(d). Dominant negative mutation
Answer Key
(1). Ans. (c). In these bacteria, the aminoacyl tRNA synthetase specific for tRNAglu also charges tRNAgln with glutamate. A second enzyme then converts the glutamate of the charged tRNAgln to glutamine.
(2). Ans. (d). The drugs which specifically target topoisomerases, usually do not affect normal fast growing cells.
(3). Ans. (a). (A) and (C)
(4). Ans. (c). Phospholipase C-β converts PI (4,5)P2 to diacylglycerol and IP3
(5). Ans. (a). P-bodies
(6). Ans. (b). H2A-H2B bind to both the entry and exit ends of DNA in nucleosomes
(7). Ans. (b). CDK1
(8). Ans. (b). Promoter clearance
(9). Ans. (c). eIF2α
(10). Ans. (d). Transferrin
(11). Ans. (a). Hedgehog protein
(12). Ans. (a). Anchoring junctions
(13). Ans. (a). The receptors are always cytosolic, where they remain associated with heat-shock proteins and have variable ligand binding domains in the N-terminal region
(14). Ans. (a). 1/6 X 10-23
(15). Ans. (c). Gain of function mutation