BSc Second Year (Sem 3 & 4) Microbiology – Daily Revision MCQ (English Medium)
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In bacterial RNA polymerase, the main role of the sigma (σ) factor is to:
Chapter 5: Transcription in Prokaryotes
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Answer: A. Recognise the promoter so transcription starts at the right place
σ factor joins the core enzyme to form the holoenzyme and lets it recognise promoter sequences for correct initiation.The Pribnow box (consensus TATAAT) in a prokaryotic promoter lies at about which position relative to the transcription start site?
Chapter 5: Transcription in Prokaryotes
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Answer: B. −10
The Pribnow box is the −10 region; the other conserved bacterial element (TTGACA) is at −35.A point mutation in which a purine is replaced by another purine (for example A → G) is called a:
Chapter 8: Mutation
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Answer: C. Transition
Purine → purine or pyrimidine → pyrimidine substitution is a transition; purine ↔ pyrimidine is a transversion.Thymine dimers formed in DNA by UV light are directly split in the presence of visible light by the enzyme:
Chapter 9: DNA Repair Mechanisms
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Answer: D. Photolyase
In photoreactivation, photolyase uses visible light energy to break the dimer bonds and restore the original thymines.Transfer of bacterial genes from one cell to another carried by a bacteriophage is called:
Chapter 10: Gene Transfer in Bacteria
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Answer: C. Transduction
Transduction uses a phage as the carrier; transformation is uptake of free DNA and conjugation needs cell-to-cell contact.Which lymphocytes complete their maturation in the thymus?
Chapter 12: Immunity
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Answer: B. T lymphocytes
T cells arise in the bone marrow but mature in the thymus, hence the name 'T'.Which class of antibody is the main antibody in body secretions such as saliva, tears and colostrum?
Chapter 13: Antigens and Antibodies
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Answer: D. IgA
Secretory IgA, a dimer with a secretory component, guards mucosal surfaces and is rich in secretions and colostrum.The classical pathway of complement activation begins when C1q binds to:
Chapter 14: The Complement System
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Answer: A. Antigen–antibody complexes
The classical pathway is antibody-dependent: C1q binds IgG or IgM bound to antigen. Mannose binding starts the lectin pathway, and spontaneous C3 hydrolysis the alternative pathway.Who first protected people against smallpox by inoculating material from cowpox lesions?
Chapter 16: Vaccines and Immunization
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Answer: D. Edward Jenner
Edward Jenner (1796) used cowpox material to protect against smallpox; the word 'vaccine' comes from vacca, Latin for cow.A disease that is constantly present at its usual level in a particular geographic area is described as:
Chapter 17: Epidemiology of Infectious Diseases
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Answer: A. Endemic
Endemic means habitually present in an area; epidemic is a rise above the expected level, pandemic is worldwide, and sporadic means occasional scattered cases.
BSc Second Year (Sem 3 & 4): MCQ in other subjects
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All questions are written by PadhaiNotes in our own words from the common syllabus of Maharashtra universities (NEP). Your own university's syllabus may differ a little.