Previous Solved GATE Life Science Questions - Microbiology

 1. Reverse transcriptase used in genetic engineering was discovered by
(a) Smith & Baltimore
(b) Temin & Baltimore
(c) Temin & Arber
(d) Smith & Arber (discovery of restriction endonucleases)
2. The evolutionary history of an organism is called
(a) Taxonomy
(b) Phylogeny
(c) Dendrogram
(d) Cladogram
3. Peptic ulcers are caused by
(a) Shigella sonei
(b) Helicobacter pylori
(c) Giardia lamblia
(d) Enterobius vermicularis
4. Which of the following species shows a high resistance to radiation damage?
(a) Deinococcus
(b) Micrococcus
(c) Staphylococcus
(d) Planococcus
5. Which group of microorganism have a high level of unsaturated fatty acids in their cell membrane?
(a) Mesophilic
(b) Psychrophilic
(c) Thermophilic
(d) Hyperthermophilic
6. Mycoplasma are different from other prokaryotes by
a) presence of chitin in cell walls
b) presence of murein in cell walls
c) presence of proteins in cell walls
d) absence of cellwall itself
7. The cell walls of gram positive bacteria contain two modified sugars, viz., N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM). They are covalently linked by
a) α-1,4-glycosidic bond
b) α-1,6-glycosidic bond
c) β-1,6-glycosidic bond
d) β-1,4-glycosidic bond
8. Selective media facilitate growth of only one kind of organism. Saboraud’s medium is used to selectively isolate
a) Coliform bacteria
b) Yeasts
c) Gram positive bacetria
d) Acid fast organisms
9. The metal ion required for the enzymatic activities of nitrogenase and nitrate reductase is
a) Molybdenum
b) Iron
c) Copper
d) Zinc
10. DNA gyrase is inhibited by
a) Tetracyclin
b) Nalidixic acid
c) Aurintricarboxylic acid
d) Cephalosporin
1. (b) Temin & Baltimore
  • Also called teminism
  • Reverse transcriptase activity: RNA dependent DNA polymerase ( to copy RNA to DNA)
  • Ribonuclease activity: to degrade RNA
  • DNA dependent DNA polymerase activity (to copy ss DNA to ds DNA)
  • Smith &Arber: discovery of restriction endonucleases (molecular scissors in rDNA technology)
2. (b) Phylogeny
  • Cladogram: a diagram that delineates the branching sequences in an evolutionary tree
  • Dendrogram: a diagram that represents relationship among groups of Taxa
  • Taxonomy: branch of science deals with identification, naming and classification of organisms.
3. (b) Helicobacter pylori
  • Shigella sonei : gram negative bacteria responsible for Shigellosis
  • Helicobacter pylori: can cause digestive illnesses, including gastritis and peptic ulcer disease.
  • Giardia lamblia: causing Giardiasis, an intestinal infection
  • Enterobius vermicularis (human pin worm intestinal parasite)
4. (a) Deinococcus
5. (b) Psychrophilic cryophilic living in extreme cold temperatures
6. d) absence of cell wall itself
  • Mycoplasma: Bacteria in the Class-Mollicutes without cellwall, pleomorphic
  • Chitinous cell wall: in fungi
  • Murien in bacteria
7. d) β-1,4-glycosidic bond
  • α-1,2-glycosidic bond: sucrose
  • α-1,4-glycosidic bond: maltose
  • α-1,6 and α-1,4-glycosidic bond: glycogen and starch
  • α-1,6-glycosidic bond: dextran
  • β-1,4-glycosidic bond: lactose, cellulose
More about, Bacteria cell wall
8. b) Yeasts
  • Sabouraud agar is a selective medium that is formulated to allow growth of fungi and inhibit the growth of bacteria.
9. a) Molybdenum
  • Mo: nitrate reductase
  • Zn: carbonic anhydrase
  • Mg: hexokinase
  • Mn: Super oxide dismutase
  • Se: Glutathione peroxidase
10. b) Nalidixic acid


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