Q.1 Which of the following techniques is commonly used to separate macromolecules based on their size and charge?
Spectrophotometry
Electrophoresis
Centrifugation
Chromatography
Explanation - Electrophoresis separates molecules like DNA, RNA, or proteins based on their size and charge using an electric field.
Correct answer is: Electrophoresis
Q.2 What is the primary purpose of a micropipette in experimental biology?
Measure pH
Transfer small volumes of liquid
Sterilize equipment
Weigh samples
Explanation - Micropipettes allow accurate measurement and transfer of microliter volumes of liquids in laboratory experiments.
Correct answer is: Transfer small volumes of liquid
Q.3 Which staining technique is most suitable for visualizing bacterial capsules?
Gram staining
Negative staining
Acid-fast staining
Endospore staining
Explanation - Negative staining stains the background and leaves capsules unstained, making them visible as clear halos around bacteria.
Correct answer is: Negative staining
Q.4 In a spectrophotometric experiment, what does the absorbance of a solution indicate?
Concentration of solute
Molecular weight
pH of solution
Viscosity
Explanation - According to Beer-Lambert law, absorbance is directly proportional to solute concentration at a specific wavelength.
Correct answer is: Concentration of solute
Q.5 Which laboratory technique is most appropriate for separating pigments from plant leaves?
Centrifugation
Paper chromatography
Gel electrophoresis
Spectrophotometry
Explanation - Paper chromatography separates pigments based on solubility and capillary action through the stationary phase (paper).
Correct answer is: Paper chromatography
Q.6 Which type of centrifugation is used to separate subcellular organelles?
Differential centrifugation
Density gradient centrifugation
Ultracentrifugation
Sedimentation centrifugation
Explanation - Differential centrifugation separates organelles based on size and density by sequentially increasing centrifugal force.
Correct answer is: Differential centrifugation
Q.7 Which method is used to sterilize heat-sensitive solutions in a laboratory?
Autoclaving
Filtration
Incineration
Boiling
Explanation - Filtration passes the solution through a membrane filter to remove microorganisms without applying heat.
Correct answer is: Filtration
Q.8 During DNA extraction, which reagent is used to precipitate DNA?
Ethanol
Phenol
Acetone
Chloroform
Explanation - Cold ethanol or isopropanol precipitates DNA from aqueous solution because DNA is insoluble in alcohol.
Correct answer is: Ethanol
Q.9 Which type of microscope is used to view live, unstained cells in high detail?
Light microscope
Electron microscope
Phase contrast microscope
Fluorescence microscope
Explanation - Phase contrast microscopes enhance contrast in transparent, unstained cells by converting phase shifts to brightness differences.
Correct answer is: Phase contrast microscope
Q.10 In enzyme kinetics, which parameter indicates the substrate concentration at which the reaction rate is half of Vmax?
Km
Vmax
kcat
pH optimum
Explanation - Km (Michaelis constant) is the substrate concentration at which the reaction rate is half of its maximum velocity.
Correct answer is: Km
Q.11 Which laboratory technique is used to amplify a specific DNA segment?
Southern blotting
PCR
Western blotting
ELISA
Explanation - Polymerase Chain Reaction (PCR) exponentially amplifies a specific DNA segment using primers and DNA polymerase.
Correct answer is: PCR
Q.12 Which method is commonly used to determine protein concentration in a solution?
Bradford assay
PCR
Gel electrophoresis
Chromatography
Explanation - The Bradford assay uses Coomassie Brilliant Blue dye, which binds to proteins and shifts absorption measurable spectrophotometrically.
Correct answer is: Bradford assay
Q.13 Which of the following is an aseptic technique in microbiology?
Flaming the loop before inoculation
Boiling culture medium
Leaving petri dish open
Shaking test tubes vigorously
Explanation - Flaming sterilizes the inoculating loop, preventing contamination when transferring microbial cultures.
Correct answer is: Flaming the loop before inoculation
Q.14 Which method is used to separate proteins based on their size in an electric field?
Isoelectric focusing
SDS-PAGE
Affinity chromatography
ELISA
Explanation - SDS-PAGE denatures proteins and applies a uniform negative charge, allowing separation based on molecular weight.
Correct answer is: SDS-PAGE
Q.15 Which indicator is used to test the presence of reducing sugars in a solution?
Benedict's solution
Biuret reagent
Methyl orange
Iodine solution
Explanation - Benedict's reagent reacts with reducing sugars under heat to form a colored precipitate, indicating their presence.
Correct answer is: Benedict's solution
Q.16 Which laboratory technique involves the use of antibodies to detect specific proteins?
PCR
Western blotting
Gel electrophoresis
Spectrophotometry
Explanation - Western blotting transfers proteins onto a membrane and uses antibodies for detection of specific proteins.
Correct answer is: Western blotting
Q.17 Which type of centrifuge is suitable for separating blood components like plasma and RBCs?
High-speed centrifuge
Low-speed centrifuge
Ultracentrifuge
Density gradient centrifuge
Explanation - Low-speed centrifugation is sufficient to separate cellular components in blood without damaging cells.
Correct answer is: Low-speed centrifuge
Q.18 In microbiology, which method is used to determine bacterial sensitivity to antibiotics?
Gram staining
Kirby-Bauer disk diffusion
PCR
Western blotting
Explanation - Disks containing antibiotics are placed on bacterial cultures to observe zones of inhibition, indicating sensitivity.
Correct answer is: Kirby-Bauer disk diffusion
Q.19 Which chemical is commonly used to fix tissues in histology?
Formalin
Ethanol
Acetic acid
Benedict's solution
Explanation - Formalin preserves tissue by cross-linking proteins and preventing degradation, allowing microscopic study.
Correct answer is: Formalin
Q.20 Which laboratory method separates DNA fragments by size for visualization?
PCR
Gel electrophoresis
ELISA
Spectrophotometry
Explanation - DNA fragments move through an agarose gel in an electric field, separating according to size for analysis.
Correct answer is: Gel electrophoresis
Q.21 Which solution is used to lyse cells in molecular biology experiments?
Lysis buffer
Benedict's solution
Formalin
Ethanol
Explanation - Lysis buffers disrupt cell membranes to release cellular contents like DNA, RNA, and proteins for analysis.
Correct answer is: Lysis buffer
Q.22 Which technique is used for detecting RNA molecules in a sample?
Northern blotting
Southern blotting
Western blotting
ELISA
Explanation - Northern blotting transfers RNA to a membrane and hybridizes with a labeled probe to detect specific sequences.
Correct answer is: Northern blotting
Q.23 Which method is used to separate molecules based on affinity to a specific ligand?
Affinity chromatography
Gel filtration
SDS-PAGE
PCR
Explanation - Affinity chromatography exploits specific binding interactions between a molecule and a ligand immobilized on a column.
Correct answer is: Affinity chromatography
Q.24 Which method is suitable for observing very small structures like viruses?
Light microscopy
Electron microscopy
Phase contrast microscopy
Fluorescence microscopy
Explanation - Electron microscopes use electron beams with much higher resolution than light, allowing visualization of viruses.
Correct answer is: Electron microscopy
Q.25 Which laboratory procedure is used to maintain microorganisms in pure culture?
Streak plate method
Gram staining
PCR
Spectrophotometry
Explanation - Streaking spreads bacteria across an agar plate to isolate single colonies for pure culture studies.
Correct answer is: Streak plate method