2017 Bacteria Viruses MCQ QP+MS

2017 Bacteria and Viruses MCQ 2017 / H2 / ACJC PRELIM / P1 Q61The diagram shows an electron micrograph of a bacterial cell. XWZYWhich of the following correctly identifies the functions of structures W, X, Y and Z?WXYZAMaintains shape of bacterial cellProtects bacterial cell against desiccationContains antibiotic resistance genes which may be beneficial to the bacterial cellServes as the site of protein synthesisBControls the passage of substances into and out of the cellMaintains shape of bacterial cellContains genetic information which is essential to the survival of bacterial cellServes as the site of translation of mRNACControls the passage of substances into and out of the cellMaintains shape of bacterial cellContains antibiotic resistance genes which may be beneficial to the bacterial cellProtects bacterial cell against desiccationDProtects bacterial Protects bacterial Contains genetic Maintains shape

cell against desiccationcell from the action of phagocytesinformation which is essential to the survival of bacterial cellof bacterial cell

2017 / H2 / ACJC PRELIM / P1 Q72The diagram below shows the enterobacteria phage P22 which is a bacteriophage that infects the bacterium Salmonella typhimurium. The genetic material and replication cycle of P22 are similar to the lambda phage. Which of the following statements can be inferred?AIt is a virulent phage which contains double-stranded RNA and undergoes the lytic cycle.BIt has a spherical envelope that is obtained when the phage buds from the host cell.CIt forms a prophage, which is replicated and passed to the daughter bacterial cells during cell division.DIt has tail fibres which allow the phage to attach to various species of host bacteria.2017 / H2 / ACJC PRELIM / P1 Q93Many of the most effective antibiotics used in modern medicine are compounds made by fungi that inhibit bacterial protein synthesis. Among the most commonly used drugs are Chloramphenicol, Cycloheximide and Rifampicin. The results of the exposure to eukaryotic and prokaryotic cells to the above three drugs are shown.Anti-microbial drugChloramphenicolCycloheximideRifampicinEukaryotic Animal CellTruncated polypeptides were found in mitochondria onlyTruncated polypeptides were found in cytosolNo protein synthesizedProkaryotic CellTruncated polypeptides were found in the cytosolTruncated polypeptides were found in the cytosolNo protein synthesizedWhich of the following shows the correct combination of the possible drug mechanisms of the above drugs?

ChloramphenicolCycloheximideRifampicinAInhibits the peptidyl transferase activity of the 70S ribosomesInhibits elongation by binding the E site of the ribosome hence preventing the release of tRNAInhibits the transcription of DNA by blocking the movement of RNA polymerase on DNABInhibits the peptidyl transferase activity of the 80S ribosomesInhibits elongation by binding the E site of the ribosome hence preventing the release of tRNAInhibits the transcription of DNA by blocking the movement of RNA polymerase on DNACInhibits elongation by binding the P site of the ribosome hence preventing the formation of peptidyl tRNAInhibits elongation by binding the A site of the ribosome hence preventing the release of tRNAInhibits translation by binding to the small ribosomal subunitDInhibits elongation by binding to mRNA and preventing ribosomal translocationInhibits elongation by binding the P site of the ribosome hence preventing the release of polypeptideInhibits translation by binding to the binding site of large ribosomal subunit 2017 / H2 / ACJC PRELIM / P1 Q124Which of the following correctly matches the state of the lac operon to the presence/absence of the molecule(s)?State of lac operonGlucoseLactosecAMP1OnPresentPresentAbsent2OnAbsentPresentAbsent3OffPresentAbsentAbsent4OnAbsentPresentPresentA1, 2, 3 and 4B1, 3 and 4 onlyC1 and 2 onlyD2 and 3 only

2017 / H2 / ACJC PRELIM / P1 Q195Salmonella typhi bacteria is known to be a viable host for a newly discovered temperate phage, but the site of prophage integration is unknown. The following gene map shows the loci of four genes on the S. typhi chromosome – arg, his, leu and cys – responsible for the biosynthesis of four essential amino acids. Four possible prophage integration sites, W, X, Y, Z are indicated.ZYWX The phages are allowed to replicate using a strain of S. typhi capable of synthesising all four amino acids (arg+ his+ leu+ cys+), and the replicated phages are then added to a mutant strain of S. typhi of genotype arg – his – leu – cys –.After a short incubation, samples of these bacteria are plated on four different media supplemented with different amino acids. The following table shows whether colonies were observed on the various media (+ indicates the presence of an amino acid in the medium while – indicates its absence).MediumSupplementation of amino acids in mediumPresence of coloniesArgHisLeuCys1–+++No2+–++No3++–+Yes4+++–YesWhich of the following is the most likely prophage integration site?ASite WBSite XCSite YDSite Z

2017 / H2 / AJC PRELIM / P1 Q116Which of the following statement comparing the human immunodeficiency virus (HIV) and lambda phage is incorrect? AThe HIV enters by receptor-mediated endocytosis, but the lambda phage infects bacterial cells by injecting its DNA.BThe capsid of the HIV enters the host cell, but the capsid of the lambda virus does not.CThe genome of the HIV must be processed before it is integrated into the host chromosome, but the genome of the lambda virus can be directly integrated.DNew HIV are released from the host cell via budding, but new lambda virus are released via cell lysis.2017 / H2 / AJC PRELIM / P1 Q127The diagram below shows the reproductive cycle of the herpes virus which causes cold sores on the mouth. With reference to the diagram below, which of the following statements best describes the herpes virus? AIt is not a retrovirus as it does not contain RNA as its genetic material

BIts mode of replication is similar to that of influenza virus.CIts replication cycle includes a lysogenic phase.DIt carries its own enzymes and ribosomes to make viral proteins.2017 / H2 / AJC PRELIM / P1 Q138What are the correct characteristics for a prokaryotic genome?PromotersDNA always bound to histone proteinsPlasmids often presentRepeat sequences absent or uncommonABCD2017 / H2 / AJC PRELIM / P1 Q149A mutant strain of E. coli has been isolated in which the lac operon is not expressed in the presence of lactose. This mutant strain was mated so that it now contains an F plasmid containing a normal lac operon. The mutant and mated strain with regard to their ᵝ-galactosidase activities in the presence and absence of lactose was compared. The following results were obtained:StrainAddition of lactoseAmount of ᵝ-galactosidase(percentage of parent strain)ParentNo0ParentYes0MatedNo0MatedYes100With respect to the results shown in table, which part of the bacterial DNA most likely is mutated?Alac A Blac I CPromoter of lac operon DOperator of lac operon

2017 / H2 / AJC PRELIM / P1 Q1510Which comparative statements about prokaryotic and eukaryotic gene expression are correct?1DNA methylation is a feature of prokaryotes but not eukaryotes.2Eukaryotes and prokaryotes both use ribosomes to translate mRNA.3Eukaryotes have introns, most prokaryotes do not.4Prokaryotes have genes organized into operons, most eukaryotes do not. A1, 2 and 3B1, 2 and 4C1, 3 and 4D2, 3 and 4 2017 / H2 / CJC PRELIM / P1 Q1511When a mutant strain of Escherichia coli that has lost the regulatory gene of its tryptophan operon is placed in a medium that contains all nutrients the cell need to grow except tryptophan, which of the following will occur?AThe cells will grow even though there is no tryptophan in the medium.BThe cells will grow until excessive tryptophan arrests the expression of the operon.CThe cells will not grow until enough tryptophan has been synthesised to make the repressor active.DThe cells will never