Chapter 2 with our Microbiology MCQs and explanations! Test your knowledge and understanding of key concepts with our complete set of multiple choice questions with detailed explanations for each answer. Increase your confidence and understanding of the fascinating world of microorganisms!
MCQs:
Microbiology MCQs 51 to 100
Who perfected a magnetic lens in 1927?
- a) Gabor
- b) Broglie
- c) None of these
- d) Busch
Explanation:
Hans Busch is regarded as the pioneer of electron optics. In 1927, he demonstrated that a magnetic field could act as a lens to focus electron beams, laying the foundation for electron microscopy and modern electron optics.
Why other options are incorrect:
Why other options are incorrect:
- • Gabor: Known for holography, not magnetic lens discovery.
- • de Broglie: Proposed matter-wave theory, not lens development.
- • None of these: Incorrect because Busch is the correct historical figure.
In electron microscope source of electrons is from?
- a) Tungsten metal
- b) Mercury lamp
- c) Both Mercury lamp and Tungsten metal
- d) None of these
Explanation:
In an electron microscope, electrons are generated from a heated tungsten filament (cathode) through thermionic emission. When the filament is heated, it releases electrons that are accelerated to form the electron beam used for imaging.
Why other options are incorrect:
Why other options are incorrect:
- • Mercury lamp: Produces ultraviolet/visible light, used in light microscopy, not electron microscopes.
- • Both Mercury lamp and Tungsten metal: Incorrect because only tungsten (or other electron sources like LaB₆) emits electrons in EM.
- • None of these: Incorrect because tungsten is the correct electron source.
Electron microscope gives magnification up to?
- a) 50,000 X
- b) 2000 X
- c) 2,00,000 X
- d) 100 X
Explanation:
Light microscopes are limited to around 1,000–2,000× magnification due to the wavelength of visible light. Electron microscopes, however, use electron beams with much shorter wavelengths, allowing magnifications of up to 200,000× or more with high resolution.
Why other options are incorrect:
Why other options are incorrect:
- • 50,000×: Lower than the maximum capability of electron microscopes.
- • 2000×: Typical upper limit of light microscopy, not electron microscopy.
- • 100×: Too low for electron microscopy applications.
If 10x and 40x objectives are used (air is the medium), the numerical aperture is?
- a) 1.8
- b) 1.0
- c) 2.0
- d) 1.5
Explanation:
Numerical Aperture (NA) is given by NA = n sin θ. When air is the imaging medium, the refractive index n = 1.0, which sets the theoretical maximum numerical aperture limit to 1.0. Therefore, even high magnification objectives like 10x and 40x cannot exceed this limit without using immersion oil.
Why other options are incorrect:
Why other options are incorrect:
- • 1.8: Exceeds the maximum possible NA in air.
- • 2.0: Physically impossible in air; requires immersion systems.
- • 1.5: Also above the limit for air as a medium.
The ability of a microscope to distinguish two objects as separate is called?
- a) Resolving power
- b) Wavelength
- c) N.A.
- d) None of these
Explanation:
Resolving power (resolution) is the ability of a microscope to distinguish two closely spaced objects as separate entities. It determines how much fine detail can be seen in a specimen.
Why other options are incorrect:
Why other options are incorrect:
- • Wavelength: Property of light, not the definition of resolving power.
- • N.A. (Numerical Aperture): A factor affecting resolution, not the definition itself.
- • None of these: Incorrect because resolving power is the correct term.
Tuberculosis is a?
- a) Arthropod borne disease
- b) Air borne disease
- c) Water borne disease
- d) Food borne disease
Explanation:
Tuberculosis (TB), caused by Mycobacterium tuberculosis, is an airborne infectious disease. It spreads through droplet nuclei released into the air when an infected person coughs, sneezes, speaks, or sings, which can then be inhaled by others.
Why other options are incorrect:
Why other options are incorrect:
- • Arthropod borne disease: Transmitted by vectors like mosquitoes or ticks, not TB.
- • Water borne disease: Spread through contaminated water (e.g., cholera).
- • Food borne disease: Spread through contaminated food (e.g., salmonellosis).
The inventor of the microscope is?
- a) Pasteur
- b) Koch
- c) Galileo
- d) Antony van Leeuwenhoek
Explanation:
Galileo Galilei is credited with building one of the earliest compound microscopes (around 1609–1610) based on optical principles similar to those used in telescopes. Later, Antony van Leeuwenhoek significantly improved lens grinding techniques and used simple microscopes to observe microorganisms.
Why other options are incorrect:
Why other options are incorrect:
- • Pasteur: Known for germ theory, not invention of microscopes.
- • Koch: Famous for Koch’s postulates and bacteriology, not microscopy invention.
- • Antony van Leeuwenhoek: Improved microscopes and discovered microorganisms, but did not invent the first microscope.
The minimum number of bacteria required to produce clinical evidence of death in a susceptible animal under standard condition is called?
- a) ID
- b) All of these
- c) MLD
- d) LD50
Explanation:
MLD (Minimum Lethal Dose) refers to the smallest quantity of a pathogen or toxin that causes death in a susceptible experimental animal under standardized conditions. It differs from LD50, which is the dose that kills 50% of a test population, and from ID, which refers to the infective dose required to establish infection rather than death.
Why other options are incorrect:
Why other options are incorrect:
- • ID: Infective dose required to cause infection, not death.
- • LD50: Lethal dose that kills 50% of a population, not the minimum lethal dose.
- • All of these: Incorrect because only MLD specifically matches the definition given.
Monoclonal antibodies are associated with the name of?
- a) Medawar
- b) Owen
- c) Burnet
- d) Köhler and Milstein
Explanation:
Georges Köhler and César Milstein developed hybridoma technology in 1975, enabling the production of monoclonal antibodies from a single B-cell clone. This breakthrough earned them the Nobel Prize in Physiology or Medicine in 1984.
Why other options are incorrect:
Why other options are incorrect:
- • Medawar: Known for immunological tolerance.
- • Owen: Discovered immune tolerance in twin calves.
- • Burnet: Proposed clonal selection theory, not monoclonal antibody production.
L – forms are discovered by?
- a) Klein Berger
- b) Louis Pasteur
- c) Robert Koch
- d) Antony van Leeuwenhoek
Explanation:
L-forms are cell wall–deficient variants of bacteria first discovered by Emmy Klieneberger-Nobel in 1935. She observed these atypical forms while working at the Lister Institute in London and named them “L-forms” after the institute. These forms can survive without a rigid cell wall under specific conditions.
Why other options are incorrect:
Why other options are incorrect:
- • Louis Pasteur: Known for fermentation and vaccination studies, not L-forms.
- • Robert Koch: Developed Koch’s postulates and identified TB bacterium, not L-forms.
- • Antony van Leeuwenhoek: First to observe microorganisms using microscopes, predates L-form discovery.
Smallpox vaccine was first discovered by?
- a) Robert Koch
- b) Edward Jenner
- c) Lister
- d) Louis Pasteur
Explanation:
Edward Jenner developed the first successful smallpox vaccine in 1796 by using cowpox material to induce immunity against smallpox. This marked the beginning of modern vaccination and laid the foundation for immunology.
Why other options are incorrect:
Why other options are incorrect:
- • Robert Koch: Known for Koch’s postulates and bacteriology.
- • Lister: Pioneer of antiseptic surgery.
- • Louis Pasteur: Developed vaccines for rabies and anthrax, but not smallpox.
In electron microscope, what material is used as an objective lense?
- a) Electrons
- b) Magnetic coils
- c) Aluminium foils
- d) Superfine glass
Explanation:
In an electron microscope, the objective lens is an electromagnetic lens made up of magnetic coils. These coils generate controlled magnetic fields that focus and direct the electron beam, since electrons cannot be focused using conventional glass lenses as in light microscopy.
Why other options are incorrect:
Why other options are incorrect:
- • Electrons: Electrons are the imaging particles, not lens material.
- • Aluminium foils: Not used for focusing electron beams.
- • Superfine glass: Glass lenses cannot control electron beams.
Father of Medical Microbiology is?
- a) Jenner
- b) Pasteur
- c) A. L. Hock
- d) Koch
Explanation:
Robert Koch is regarded as the Father of Medical Microbiology. He formulated Koch’s postulates and identified the causative agents of major infectious diseases such as tuberculosis, cholera, and anthrax, establishing a scientific basis for bacteriology.
Why other options are incorrect:
Why other options are incorrect:
- • Jenner: Father of vaccination.
- • Pasteur: Father of microbiology and germ theory.
- • A. L. Hock: Not recognized as Father of Medical Microbiology.
Eye cannot resolve any image less than?
- a) 1µm
- b) 2µm
- c) 5µm
- d) 7µm
Explanation:
The resolving power of the human eye is limited by the spacing of photoreceptor cells in the retina. Under typical laboratory and microbiology references, the practical limit of resolution is around 5–10 µm for distinguishing small objects. Anything smaller than this cannot be clearly resolved without magnification using a microscope.
Why other options are incorrect:
Why other options are incorrect:
- • 1 µm: Below the realistic resolving capability of the unaided human eye.
- • 2 µm: Still too small to be resolved without optical aid.
- • 7 µm: Within a broad range, but standard MCQ reference value is 5 µm.
Modern concept of chemotherapy was proposed by?
- a) Paul Ehrlich
- b) Elie Metchnikoff
- c) Joseph Lister
- d) None of these
Explanation:
Paul Ehrlich is considered the father of modern chemotherapy. He introduced the concept of a “magic bullet,” a compound that selectively targets and destroys pathogens without damaging host cells, laying the foundation for antimicrobial drug development.
Why other options are incorrect:
Why other options are incorrect:
- • Elie Metchnikoff: Known for phagocytosis and innate immunity.
- • Joseph Lister: Pioneer of antiseptic surgery.
- • None of these: Incorrect because Ehrlich is the correct answer.
Viral infection of bacteria was discovered by?
- a) Beijerinck
- b) De’Herelle
- c) Ivanowsky
- d) F.W. Twort
Explanation:
The phenomenon of viral infection of bacteria was first observed by Frederick W. Twort in 1915, when he noticed a “glassy transformation” in bacterial colonies, later understood as bacteriophage activity. Later, Félix d’Hérelle independently confirmed the discovery in 1917 and introduced the term bacteriophage.
Why other options are incorrect:
Why other options are incorrect:
- • Beijerinck: Proposed the concept of “contagium vivum fluidum” for viruses but did not discover bacteriophages.
- • De’Herelle: Discovered bacteriophages independently later and named them, but not the first observer.
- • Ivanowsky: Discovered filterable agents causing tobacco mosaic disease, not bacteriophages.
The resolving power of the compound microscope is?
- a) 0.2 micron
- b) 0.2 Angstrom units
- c) 0.2 millimeter
- d) 0.2 centimeter
Explanation:
The resolving power (resolution limit) of a standard compound light microscope is approximately 0.2 micrometers (µm). This limit is determined by the wavelength of visible light and the numerical aperture of the objective lens system.
Why other options are incorrect:
Why other options are incorrect:
- • 0.2 Å (Angstrom): Too small; below the physical limit of light microscopy.
- • 0.2 mm: Far too large for microscopic resolution.
- • 0.2 cm: Macroscopic scale, not microscopic resolution.
The role of phagocytosis was discovered by?
- a) Paul Ehrlich
- b) Joseph Lister
- c) Pasteur
- d) Elie Metchnikoff
Explanation:
Elie Metchnikoff discovered the process of phagocytosis in 1882 while studying starfish larvae. He observed specialized cells that engulf and digest foreign particles, establishing the foundation of cellular immunity and innate immune response.
Why other options are incorrect:
Why other options are incorrect:
- • Paul Ehrlich: Known for antibody theory and chemotherapy, not phagocytosis discovery.
- • Joseph Lister: Pioneer of antiseptic surgery.
- • Pasteur: Developed germ theory and vaccines, but did not discover phagocytosis.
In electron microscope, the source of electrons is?
- a) Mercury lamp
- b) Tungsten filament
- c) None of these
- d) Mercury lamp and Tungsten metal
Explanation:
In an electron microscope, electrons are produced from a heated tungsten filament (electron gun) via thermionic emission. These electrons are accelerated under high voltage and focused into a beam to produce highly magnified and high-resolution images.
Why other options are incorrect:
Why other options are incorrect:
- • Mercury lamp: Used in light microscopes for illumination, not for electron generation.
- • None of these: Incorrect because tungsten filament is the correct electron source.
- • Mercury lamp and Tungsten metal: Mercury lamp does not produce electrons in microscopy systems.
The main feature of prokaryotic organism is?
- a) Absence of locomotion
- b) Absence of nuclear envelope
- c) Absence of protein synthesis
- d) Absence of nuclear material
Explanation:
The key feature of prokaryotic organisms is the absence of a membrane-bound nuclear envelope. Their genetic material (DNA) is present in a nucleoid region but is not enclosed within a true nucleus, unlike eukaryotic cells.
Why other options are incorrect:
Why other options are incorrect:
- • Absence of locomotion: Many prokaryotes are motile using flagella.
- • Absence of protein synthesis: Prokaryotes actively perform protein synthesis using ribosomes.
- • Absence of nuclear material: DNA is present, just not membrane-bound.
What is the useful magnification range of a light microscope?
- a) 500x – 1000x
- b) 1000x – 5000x
- c) 1000x – 2000x
- d) None of these
Explanation:
The useful magnification range of a standard light microscope is approximately 1000x to 2000x. Beyond this range, empty magnification occurs, where the image appears larger but no additional structural detail is resolved due to the diffraction limit of visible light.
Why other options are incorrect:
Why other options are incorrect:
- • 500x – 1000x: Too low; does not represent the full capability of high-power light microscopy.
- • 1000x – 5000x: Exceeds practical limit; resolution does not improve beyond ~2000x.
- • None of these: Incorrect because 1000x–2000x is the accepted useful range.
Father of microbiology is?
- a) Lister
- b) Robert Koch
- c) Louis Pasteur
- d) A.V. Leeuwenhoek
Explanation:
Antonie van Leeuwenhoek is regarded as the Father of Microbiology because he was the first scientist to observe and describe microorganisms, which he called “animalcules,” using simple single-lens microscopes that he constructed himself.
Why other options are incorrect:
Why other options are incorrect:
- • Lister: Known for antiseptic surgery.
- • Robert Koch: Established Koch’s postulates and identified disease-causing bacteria.
- • Louis Pasteur: Discovered fermentation and developed vaccines.
Who is known as the Father of Medical Microbiology?
- a) Jenner
- b) Koch
- c) A.L. Hock
- d) Pasteur
Explanation:
Robert Koch is regarded as the Father of Medical Microbiology. He established Koch’s postulates, which are fundamental criteria used to identify the causative agents of infectious diseases such as tuberculosis, anthrax, and cholera.
Why other options are incorrect:
Why other options are incorrect:
- • Jenner: Known for developing the smallpox vaccine, not medical microbiology foundation.
- • A.L. Hock: Incorrect name / not recognized in microbiology history.
- • Pasteur: Father of modern microbiology, but Koch is specifically credited for medical microbiology.
The term mutation was coined by?
- a) Pasteur
- b) Hugo de Vries
- c) Darwin
- d) Lamarck
Explanation:
The term “mutation” was introduced by Hugo de Vries in 1901. He proposed the Mutation Theory of evolution after observing sudden heritable changes in the evening primrose (Oenothera lamarckiana), suggesting that new species could arise through abrupt genetic changes.
Why other options are incorrect:
Why other options are incorrect:
- • Pasteur: Known for germ theory and vaccination.
- • Darwin: Proposed natural selection, not the term mutation.
- • Lamarck: Proposed inheritance of acquired characteristics.
In which materials did Pasteur first conduct fermentation experiments?
- a) Milk
- b) Fruit juices
- c) Both milk and fruit juices
- d) Food material
Explanation:
Louis Pasteur investigated fermentation in both milk and fruit juices. He studied lactic acid fermentation in milk and alcoholic fermentation in fruit juices, helping establish that specific microorganisms are responsible for specific fermentation processes.
Why other options are incorrect:
Why other options are incorrect:
- • Milk: Only covers lactic fermentation, not full scope of Pasteur’s experiments.
- • Fruit juices: Only covers alcoholic fermentation, incomplete answer.
- • Food material: Too general and not specific to Pasteur’s experiments.
Source of light in fluorescence microscopy is from?
- a) Both Mercury lamp and Sunlight
- b) Mercury lamp
- c) Sunlight
- d) None of these
Explanation:
Fluorescence microscopy requires a high-intensity light source to excite fluorophores within the specimen. A high-pressure mercury vapor lamp (or xenon arc lamp) is commonly used because it emits strong light at specific excitation wavelengths needed to produce fluorescence.
Why other options are incorrect:
Why other options are incorrect:
- • Both Mercury lamp and Sunlight: Sunlight is not controlled or sufficiently specific for microscopy.
- • Sunlight: Not suitable due to inconsistency and lack of required intensity.
- • None of these: Incorrect because mercury lamps are standard sources.
Which type of mutation produces a termination (stop) codon?
- a) Missense mutation
- b) Reverse mutation
- c) Nonsense mutation
- d) Neutral mutation
Explanation:
A nonsense mutation is a point mutation in which a codon is changed into a stop (termination) codon. This causes premature termination of protein synthesis, usually producing a shortened and nonfunctional protein.
Why other options are incorrect:
Why other options are incorrect:
- • Missense mutation: Changes one amino acid into another, but does not create a stop codon.
- • Reverse mutation: Restores the original sequence, reversing a previous mutation.
- • Neutral mutation: Does not significantly affect protein function or structure.
Compound microscope was discovered by?
- a) Janssen & Hans
- b) None of these
- c) Antony van Leeuwenhoek
- d) Pasteur
Explanation:
The compound microscope was developed around 1590 by Dutch spectacle makers Hans Janssen and his son Zacharias Janssen. Their design combined multiple lenses to achieve higher magnification, forming the basis of modern compound microscopy.
Why other options are incorrect:
Why other options are incorrect:
- • None of these: Incorrect because Janssen & Hans are credited with the invention.
- • Antony van Leeuwenhoek: Improved single-lens microscopes, not compound type.
- • Pasteur: Worked in microbiology but did not invent microscopes.
What is the term for the ability of a specific strain of a microorganism to cause disease?
- a) Pathogen
- b) Infection
- c) Virulence
- d) None of these
Explanation:
Virulence is the degree of pathogenicity of a microorganism, describing how severe or harmful a particular strain is in causing disease. It reflects the intensity of infection and damage caused to the host.
Why other options are incorrect:
Why other options are incorrect:
- • Pathogen: A microorganism that can cause disease, not the measure of its strength.
- • Infection: The process of invasion and multiplication of pathogens in the host.
- • None of these: Incorrect because virulence is the correct term.
Mesosomes are also known as?
- a) Plasmids
- b) Chondroids
- c) Mitochondria
- d) Endoplasmic reticulum
Explanation:
Mesosomes (also called chondroids in older terminology) are infoldings of the bacterial plasma membrane. They were once thought to be involved in respiration and cell division, and were compared functionally to mitochondria. However, modern studies suggest they may be artifacts of chemical fixation in electron microscopy rather than true cellular structures.
Why other options are incorrect:
Why other options are incorrect:
- • Plasmids: Extrachromosomal DNA, not membrane structures.
- • Mitochondria: Eukaryotic organelles, not bacterial mesosomes.
- • Endoplasmic reticulum: Eukaryotic intracellular membrane system.
Compound Microscope was discovered by?
- a) A.V. Lewenhoek
- b) Pasteur
- c) Janssen and Hans
- d) None of these
Explanation:
The compound microscope was first developed around 1590 by Dutch spectacle makers Zacharias Janssen and Hans Janssen. It used a combination of lenses to achieve higher magnification than single-lens microscopes.
Why other options are incorrect:
Why other options are incorrect:
- • A.V. Leeuwenhoek: Improved simple microscopes and first observed microorganisms, but did not invent the compound microscope.
- • Pasteur: Known for germ theory and vaccination, not microscopy invention.
- • None of these: Incorrect because Janssen and Hans are historically credited.
Electron Microscope was discovered by?
- a) Knoll and Ruska
- b) Prof. Fritz
- c) Janssen and Hans
- d) None of these
Explanation:
The electron microscope was developed by Ernst Ruska and Max Knoll in 1931. They designed the first practical electron microscope by using electron optics instead of light, greatly increasing magnification beyond the limits of light microscopy. Ruska later received the Nobel Prize in Physics in 1986 for this pioneering work.
Why other options are incorrect:
Why other options are incorrect:
- • Prof. Fritz: Not associated with electron microscope invention.
- • Janssen and Hans: Developed the compound light microscope, not electron microscope.
- • None of these: Incorrect because Knoll and Ruska are correct inventors.
Lederberg and Tatum (1946) described the phenomena of?
- a) Conjunction
- b) Transformation
- c) Plasmids
- d) Mutation
Explanation:
Lederberg and Tatum (1946) demonstrated bacterial conjugation, a process in which genetic material is transferred directly from one bacterial cell to another through cell-to-cell contact. This discovery established one of the major mechanisms of horizontal gene transfer in bacteria.
Why other options are incorrect:
Why other options are incorrect:
- • Transformation: Discovered by Griffith (1928), involves uptake of free DNA from the environment.
- • Plasmids: Discovered later as extra-chromosomal DNA elements, not the phenomenon described in 1946.
- • Mutation: A general genetic change, not a specific mechanism discovered by Lederberg and Tatum.
The causative organism of rocky mountain spotted fever was first described by?
- a) Robert Koch
- b) da Rocha-Lima
- c) Howard Ricketts
- d) Both Howard Ricketts and da Rocha-Lima
Explanation:
Howard Taylor Ricketts first identified the causative agent of Rocky Mountain Spotted Fever, later named Rickettsia rickettsii. After his death, Henrique da Rocha-Lima contributed to the classification of these organisms and proposed the genus name Rickettsia in honor of Ricketts, helping establish their role in rickettsial diseases.
Why other options are incorrect:
Why other options are incorrect:
- • Robert Koch: Known for Koch’s postulates and TB discovery, not RMSF.
- • da Rocha-Lima: Contributed to classification but did not first describe the organism alone.
- • Howard Ricketts: Correct, but historically the discovery and naming process involved multiple contributors.
Disease that affects many people at different countries is termed as?
- a) Epidemic
- b) Pandemic
- c) Endemic
- d) Sporadic
Explanation:
A pandemic is an epidemic that spreads across multiple countries or continents, affecting a large population globally. It represents the highest level of disease spread compared to epidemic and endemic conditions.
Why other options are incorrect:
Why other options are incorrect:
- • Epidemic: Restricted to a specific region or community.
- • Endemic: Constant presence of disease in a particular area.
- • Sporadic: Occurs irregularly and infrequently.
The stalked particles on the cristae of mitochondria are called?
- a) Oxysomes
- b) Spherosomes
- c) Glyoxysomes
- d) Peroxisomes
Explanation:
Oxysomes (also known as F₀–F₁ particles or ATP synthase complexes) are stalked structures present on the inner mitochondrial membrane (cristae). They are directly involved in oxidative phosphorylation and ATP production.
Why other options are incorrect:
Why other options are incorrect:
- • Spherosomes: Lipid storage bodies found in plant cells.
- • Glyoxysomes: Specialized peroxisomes involved in fat metabolism in plants.
- • Peroxisomes: Organelles involved in detoxification, not ATP synthesis.
Term vaccine was coined by?
- a) Pasteur
- b) Needham
- c) Robert Koch
- d) None of these
Explanation:
Louis Pasteur coined the term “vaccine” and “vaccination” in 1881. He used it to describe his method of using weakened (attenuated) microorganisms to induce immunity, extending Jenner’s work on smallpox to other infectious diseases.
Why other options are incorrect:
Why other options are incorrect:
- • Needham: Known for spontaneous generation experiments, not vaccination terminology.
- • Robert Koch: Established germ theory and Koch’s postulates, but did not coin the term vaccine.
- • None of these: Incorrect because Pasteur is historically credited.
The antiseptic method was first demonstrated by?
- a) Beijerinck
- b) Edward Jenner
- c) Iwanowski
- d) Lord Lister
Explanation:
Lord Joseph Lister is regarded as the pioneer of antiseptic surgery. He introduced the use of carbolic acid (phenol) to sterilize surgical instruments and disinfect wounds, significantly reducing post-surgical infections and mortality rates.
Why other options are incorrect:
Why other options are incorrect:
- • Beijerinck: Known for enrichment culture technique and microbiology advancements.
- • Edward Jenner: Developed the smallpox vaccine (vaccination).
- • Iwanowski: Discovered the tobacco mosaic virus (TMV).
Phagocytic phenomenon was discovered by?
- a) Alexander Fleming
- b) Louis Pasteur
- c) Robert Koch
- d) Metchnikof
Explanation:
Élie Metchnikoff discovered phagocytosis in 1882. He demonstrated that certain cells of the immune system (phagocytes) can engulf and destroy foreign particles and microbes, forming the basis of cellular immunity.
Why other options are incorrect:
Why other options are incorrect:
- • Alexander Fleming: Discovered penicillin, not phagocytosis.
- • Louis Pasteur: Developed germ theory and vaccines.
- • Robert Koch: Identified disease-causing bacteria and established Koch’s postulates.
Prophylaxis of cholera is?
- a) Protected water supply
- b) Environmental sanitation
- c) Immunization with killed vaccines
- d) All of these
Explanation:
Cholera prevention (prophylaxis) relies on multiple strategies including provision of safe drinking water, proper environmental sanitation to prevent fecal–oral transmission, and vaccination with killed or inactivated vaccines in endemic or high-risk areas.
Why other options are also correct:
Why other options are also correct:
- • Protected water supply: Prevents ingestion of contaminated water carrying Vibrio cholerae.
- • Environmental sanitation: Reduces spread from contaminated waste and surfaces.
- • Immunization with killed vaccines: Provides active immunity in at-risk populations.
Light gathering capacity of Microscope is called?
- a) Numerical aperture
- b) Angular aperture
- c) Both Numerical aperture and Angular aperture
- d) None of these
Explanation:
Numerical aperture (NA) defines the light-gathering ability of a microscope objective lens. It depends on the refractive index of the medium and the sine of the half-angle of the light cone entering the lens, and it directly influences resolution and brightness.
Why other options are incorrect:
Why other options are incorrect:
- • Angular aperture: Refers only to the angle of light cone, not full light-gathering capacity.
- • Both Numerical aperture and Angular aperture: Angular aperture is a component, not the complete measure.
- • None of these: Incorrect because NA is the correct term.
The term bacteriophage was coined by?
- a) d’Herelle
- b) Iwanowski
- c) Beijerinck
- d) F.W. Twort
Explanation:
Although Frederick Twort first observed bacterial lysis in 1915, Félix d’Herelle independently confirmed the phenomenon in 1917 and coined the term bacteriophage, meaning “bacteria eater,” for viruses that infect bacteria.
Why other options are incorrect:
Why other options are incorrect:
- • Iwanowski: Discovered tobacco mosaic virus.
- • Beijerinck: Developed enrichment culture technique and virus concept.
- • F.W. Twort: First observed bacteriophage-like agents but did not coin the term.
Antiseptic methods were first introduced by?
- a) Beijernick
- b) Lord Lister
- c) Iwanowski
- d) Edward Jenner
Explanation:
Lord Joseph Lister introduced antiseptic surgery in the 1860s using carbolic acid (phenol) to disinfect surgical instruments, wounds, and operating environments. This significantly reduced surgical infections and established modern antiseptic techniques.
Why other options are incorrect:
Why other options are incorrect:
- • Beijerinck: Known for enrichment culture technique and virology studies.
- • Iwanowski: Discovered the tobacco mosaic virus.
- • Edward Jenner: Developed the first smallpox vaccine.
Condensation of light in a light microscope is done by?
- a) Ocular
- b) Condenser
- c) Objective
- d) All of these
Explanation:
The condenser is an optical component of a light microscope located below the stage. It collects and focuses (condenses) light from the illumination source onto the specimen, improving resolution and contrast.
Why other options are incorrect:
Why other options are incorrect:
- • Ocular: Magnifies the final image, does not condense light.
- • Objective: Forms the primary magnified image, not responsible for light condensation.
- • All of these: Incorrect because only the condenser performs this function.
The magnification power of electron microscope developed by Knoll and Ruska is?
- a) 15,000x
- b) 12,000x
- c) 20,000x
- d) 10,000x
Explanation:
Max Knoll and Ernst Ruska built the first electron microscope prototype in 1931, achieving a magnification of about 12,000×. This breakthrough demonstrated the potential of electron optics and led to modern electron microscopes with extremely high resolving power and magnification.
Why other options are incorrect:
Why other options are incorrect:
- • 15,000×: Not the reported magnification of the first prototype.
- • 20,000×: Higher than early experimental capability.
- • 10,000×: Below the documented performance of Knoll and Ruska’s prototype.
Griffith (1928) reported the phenomenon of transformation first in?
- a) E. coli
- b) H. influenzae
- c) Bacillus species
- d) Pneumococci
Explanation:
Frederick Griffith first demonstrated bacterial transformation in 1928 using Streptococcus pneumoniae (pneumococci). He showed that a “transforming principle” from heat-killed virulent bacteria could convert non-virulent strains into virulent ones—later identified as DNA.
Why other options are incorrect:
Why other options are incorrect:
- • E. coli: Used later in molecular genetics, not Griffith’s experiment.
- • H. influenzae: Studied in transformation by Avery’s era, not Griffith.
- • Bacillus species: Not involved in the original transformation experiment.
Hybridoma technique was first discovered by?
- a) Land Steiner
- b) Robert Koch
- c) ‘D’ Herelle
- d) Kohler and Milstein
Explanation:
The hybridoma technique was developed by Georges Köhler and César Milstein in 1975. It involves fusing a specific antibody-producing B-lymphocyte with a myeloma cell to create immortal hybrid cells (hybridomas) that continuously produce monoclonal antibodies.
Why other options are incorrect:
Why other options are incorrect:
- • Landsteiner: Discovered blood groups, not hybridoma technique.
- • Robert Koch: Known for Koch’s postulates and germ theory.
- • d’Herelle: Discovered bacteriophages.
Antiseptic surgery was discovered by?
- a) Ernest Abbe
- b) Beijerinck
- c) Pasteur
- d) Joseph Lister
Explanation:
Joseph Lister is known as the Father of Modern Surgery. He introduced antiseptic surgical techniques based on Louis Pasteur’s germ theory by using carbolic acid (phenol) to sterilize instruments and disinfect wounds, significantly reducing post-operative infections.
Why other options are incorrect:
Why other options are incorrect:
- • Ernest Abbe: Known for contributions to microscopy optics.
- • Beijerinck: Pioneer of virology and enrichment culture techniques.
- • Pasteur: Developed germ theory and pasteurization, not antiseptic surgery.
In electron microscope, the source of electrons is from?
- a) Mercury lamp
- b) Tungsten filament
- c) LED light source
- d) Halogen bulb
Explanation:
The electron microscope uses a tungsten filament (electron gun) as the electron source. When heated, it emits electrons through thermionic emission, forming a focused electron beam used for imaging.
Why other options are incorrect:
Why other options are incorrect:
- • Mercury lamp: Used in fluorescence microscopy, not electron microscopes.
- • LED light source: Used in light microscopes and imaging devices, not electron beam systems.
- • Halogen bulb: Used in optical microscopes, not electron generation.
During conjugation, genetic material is transferred through?
- a) Pili
- b) Capsule
- c) Medium
- d) Cell wall
Explanation:
During bacterial conjugation, genetic material (usually plasmid DNA) is transferred from a donor cell to a recipient cell through a specialized structure called the sex pilus (F pilus). This pilus forms a direct bridge that allows DNA transfer between the two cells.
Why other options are incorrect:
Why other options are incorrect:
- • Capsule: Protective outer layer, not involved in DNA transfer.
- • Medium: Conjugation requires direct cell-to-cell contact.
- • Cell wall: Structural component, not a transfer channel.
One Comment