← Combined Technical (NG)
Past Questions — 2026
DNA finger printing is based on unique:
A)
Coding sequences
B)
Tandem repeats
C)
Mutant genes
D)
Duplication of genes
DNA fingerprinting is based on polymorphisms in repetitive DNA regions, especially Variable Number Tandem Repeats (VNTRs) and Short Tandem Repeats (STRs). These tandem repeats vary greatly among individuals, making them useful for identification.
Why others are incorrect: (a) Coding sequences are generally more conserved and not sufficiently variable for fingerprinting. (c) Mutant genes are not the basis of routine DNA profiling. (d) Gene duplication is not the principle used in DNA fingerprinting.
Which of the following is considered the earliest form of life?
A)
Fungal forms
B)
Multicellular organisms
C)
Prokaryotic microbes
D)
Viruses
The earliest known life forms on Earth were simple single-celled prokaryotes, such as ancient bacteria-like organisms. They appeared much earlier than multicellular organisms and fungi, which evolved later as more complex life forms. Viruses are generally not considered the earliest form of life because they are acellular and depend on host cells for replication, so they are usually not classified as truly living organisms. Therefore, option (c) is correct.
Normal serum electrolyte level of potassium is :
A)
3.5-5 mmol/L
B)
3.5-5 nm/L
C)
136-145 mmol/L
D)
146-166 mml/L
The normal serum potassium level in adults is about 3.5-5.0 mmol/L (or mEq/L). Therefore, option (a) is correct. Option (b) is incorrect because the unit 'nm/L' is wrong. Option (c) 136-145 mmol/L is the normal range for serum sodium, not potassium. Option (d) 146-166 mml/L is also not the normal potassium range and uses an incorrect unit.
The following enzymes are all tumor markers, EXCEPT :
A)
PSA
B)
Acid phosphatase
C)
Amylase
D)
Neuron specific enolase
Tumor markers are substances used to help detect or monitor certain cancers. PSA is a well-known marker for prostate cancer, acid phosphatase has been used as a marker in carcinoma prostate, and neuron specific enolase is a marker for neuroendocrine tumors such as small cell lung cancer and neuroblastoma. Amylase is primarily a digestive enzyme used in the diagnosis of pancreatic disorders like pancreatitis, not a standard tumor marker. Therefore, the exception is amylase.
Repeated cycles of PCR consist of:
A)
Denaturation Annealing Extension
B)
Cooling Heating Cooling only
C)
Transcription Translation Replication
D)
Annealing Denaturation Digestion
PCR (Polymerase Chain Reaction) is carried out in repeated thermal cycles with three main steps: (1) Denaturation – the double-stranded DNA is heated to separate into single strands, (2) Annealing – primers bind to the target DNA sequence at a lower temperature, and (3) Extension – DNA polymerase extends the primers to synthesize new DNA strands. Hence option (a) is correct. Option (b) is incorrect because it is incomplete and does not describe the actual biochemical steps. Option (c) is incorrect because transcription and translation are gene expression processes, not PCR steps. Option (d) is incorrect because the order is wrong and digestion is not a standard PCR step.
Reducing sugars are differentiated from non reducing sugars by:
A)
Iodine Test
B)
Seliwanoff’s Test
C)
Molisch’s Test
D)
Benedict’s Test
Benedict’s test is used to distinguish reducing sugars from non-reducing sugars. Reducing sugars have a free aldehyde or ketone group that can reduce copper(II) ions in Benedict’s reagent to copper(I) oxide, producing a color change/precipitate. Non-reducing sugars do not give this reaction unless first hydrolysed.
Why others are incorrect: Iodine test is for starch, Seliwanoff’s test distinguishes ketoses from aldoses, and Molisch’s test is a general test for carbohydrates.
A facultative parasite is one that:
A)
Must live within a host
B)
Lives on the surface of the host
C)
Cannot survive without a specific vector
D)
Can exist both freely and as a parasite
A facultative parasite is an organism that is normally free-living but can become parasitic under certain conditions. Therefore, it can exist both independently and as a parasite.
Why others are incorrect:
(a) 'Must live within a host' describes an obligate parasite, not a facultative one.
(b) 'Lives on the surface of the host' describes an ectoparasite.
(c) 'Cannot survive without a specific vector' refers to vector dependence, not facultative parasitism.
Indian ink for CSF is used for detection of:
A)
Aspergillus
B)
Cryptoccocus
C)
Dermatophytes
D)
Blastomycosis
Indian ink preparation of cerebrospinal fluid (CSF) is classically used to detect Cryptococcus, especially Cryptococcus neoformans, because its thick polysaccharide capsule appears as a clear halo against the dark background.
Why others are incorrect:
- Aspergillus: usually detected by culture, microscopy, galactomannan, or histopathology, not Indian ink CSF.
- Dermatophytes: infect skin, hair, and nails; diagnosed by KOH mount/culture, not CSF Indian ink.
- Blastomycosis: diagnosed by tissue microscopy/culture/antigen tests, not typically by Indian ink CSF.
Therefore, the correct answer is option (b).
The best method to prevent Hepatitis A infection is:
A)
Antibiotics
B)
Live attenuated vaccine
C)
Recombinant DNA vaccine
D)
Proper sanitation and inactivated vaccine
Hepatitis A spreads mainly by the faeco-oral route through contaminated food and water. Therefore, the most effective prevention includes good sanitation, safe drinking water, hygiene, and vaccination. The Hepatitis A vaccine used routinely is an inactivated (killed) vaccine. Antibiotics do not work against viral infections, live attenuated vaccine is not the standard answer here, and recombinant DNA vaccine is used for Hepatitis B, not Hepatitis A.
Immunofluorescence test is based on the use of:
A)
Radioactive isotopes
B)
Fluorescent-labeled antibodies
C)
Enzyme-substrate reaction
D)
Heat fixation
Immunofluorescence is a serological/immunological technique in which antibodies are tagged with fluorescent dyes (such as fluorescein). These labeled antibodies bind specifically to antigens, and the fluorescence can then be seen under a fluorescence microscope. Therefore, the test is based on fluorescent-labeled antibodies.
Why others are incorrect: Radioactive isotopes are used in radioimmunoassay, not immunofluorescence. Enzyme-substrate reaction is the basis of ELISA/immunoenzyme tests. Heat fixation is only a specimen preparation step and not the principle of the test.
Which of the following protein was first sequenced by Frederick Sanger?
A)
Myosin
B)
Insulin
C)
Myoglobin
D)
Haemoglobin
Frederick Sanger was the first scientist to determine the complete amino acid sequence of a protein, and that protein was insulin. This landmark work showed that proteins have a definite chemical structure and earned him the Nobel Prize in Chemistry in 1958. The other options are incorrect: myosin is a muscle protein not first sequenced by Sanger, myoglobin was later structurally studied by other researchers, and haemoglobin was also not the first protein sequenced by him.
Who is the father of modern biochemistry?
A)
Carl Neuberg
B)
Justus von liebig
C)
Felix Hoppe
D)
Strasbourg
Carl Neuberg is widely known as the father of modern biochemistry because of his pioneering work in biochemical research, especially in enzyme chemistry and metabolism. Justus von Liebig is often called the father of agricultural chemistry, not modern biochemistry. Felix Hoppe-Seyler is an important founder of biochemistry as a discipline, but the title 'father of modern biochemistry' is generally attributed to Carl Neuberg. Strasbourg is a place, not a scientist.
Fouchet’s test in urine is used to detect:
A)
Ketone bodies
B)
Urobilinogen
C)
Fructose
D)
Bilirubin
Fouchet’s test is used to detect bile pigments, especially bilirubin, in urine. In this test, bilirubin is oxidized to biliverdin, producing a green/blue-green color. Therefore, option (d) is correct. The other options are incorrect because ketone bodies are detected by Rothera’s test, urobilinogen by Ehrlich’s aldehyde reaction, and fructose by Seliwanoff’s test.
One of the best methods to determine the number of bacteria present per ml of liquid broth/ specimen is:
A)
Pour plate method
B)
Spread plate method
C)
Liquid culture
D)
Streak plate method
The pour plate method is one of the best methods for determining the number of viable bacteria per ml of a liquid specimen because a measured volume of diluted sample is mixed with molten agar and colonies are counted after incubation. This allows estimation of colony-forming units (CFU/ml). The spread plate method also helps in counting viable cells, but only a small volume is spread on the surface, so pour plate is classically preferred in such exam questions for bacterial count per ml. Liquid culture is used for growth, not accurate counting, and streak plate is mainly used for isolation of pure colonies, not enumeration.
WIDAL test detects:
A)
Antigen–antibody precipitation
B)
O and H agglutinins
C)
Salmonella DNA
D)
Typhoid toxin
The Widal test is a serological agglutination test used for diagnosing enteric fever (typhoid/paratyphoid). It detects antibodies in the patient's serum against the O (somatic) and H (flagellar) antigens of Salmonella typhi. Therefore, it detects O and H agglutinins.
Why others are incorrect: (a) Widal is based on agglutination, not precipitation; (c) Salmonella DNA is detected by molecular tests like PCR, not Widal; (d) Widal does not detect any typhoid toxin.
Transmission of genes from one bacterium to another neighbour bacterium is known as:
A)
Vertical gene transfer
B)
Horizontal gene transfer
C)
Mutation
D)
Transduction
Gene transfer from one bacterium to another neighbouring bacterium is called horizontal gene transfer, because the genes move between organisms of the same generation rather than from parent to offspring. Vertical gene transfer is inheritance from parent to daughter cells. Mutation is a change in genetic material, not transfer between bacteria. Transduction is only one specific type of horizontal gene transfer mediated by bacteriophages, so the broader correct answer is horizontal gene transfer.
Commonly used confirmatory diagnostic test for Western blot is:
A)
Hepatitis A
B)
HIV
C)
Influenza
D)
Tuberculosis
Western blot has been commonly used as a confirmatory test for HIV infection after an initial screening test such as ELISA. It detects antibodies against specific HIV proteins, making it useful for confirmation. The other options are incorrect because Western blot is not the commonly used confirmatory diagnostic test for Hepatitis A, Influenza, or Tuberculosis.
Southern blotting analysis is used for all, EXCEPT :
A)
Detecting the presence of mutant gene
B)
Visualising DNA profile
C)
Studying a microarray
D)
Detecting restriction fragment length polymorphism
Southern blotting is a technique used to detect specific DNA sequences in DNA fragments after gel electrophoresis and transfer to a membrane. It is used for detecting mutant genes, analysing DNA profiles, and identifying restriction fragment length polymorphism (RFLP). Microarray analysis is a different high-throughput hybridization technique performed on chips or slides, not by Southern blotting. Therefore, the exception is option (c).
Distilled water is a poor conductor of electricity because it lacks:
A)
Air
B)
Salts and minerals
C)
Hydrogen ions
D)
Pure H2O molecules
Electric current in water is conducted mainly by dissolved ions. Distilled water is nearly free from dissolved salts and minerals, so it has very few ions to carry electricity and is therefore a poor conductor. Option (a) is irrelevant. Option (c) is incorrect because pure water has a very small number of H+ and OH− ions due to self-ionization, but not enough for good conduction. Option (d) is incorrect because distilled water is made of pure H2O molecules; the problem is the absence of dissolved ionic impurities.
Which of the following measures the ability of the liver to synthesize clotting factors?
A)
AST/ALT
B)
Alkaline phosphatase
C)
Bilirubin
D)
INR
INR (International Normalized Ratio) reflects prothrombin time and is used to assess the liver’s synthetic function because the liver produces several clotting factors. When liver synthesis is impaired, INR becomes prolonged. AST/ALT indicate hepatocellular injury, alkaline phosphatase suggests cholestasis, and bilirubin reflects excretory/metabolic function rather than clotting factor synthesis.
Housefly acts as mechanical vector for transmission of all of the following infections, EXCEPT:
A)
Amoebiasis
B)
Typhoid
C)
Cholera
D)
Hepatitis B
Houseflies are mechanical vectors that carry pathogens externally on their body parts or internally in the gut and contaminate food and water. They commonly spread intestinal infections such as amoebiasis, typhoid, and cholera. Hepatitis B, however, is not transmitted mechanically by houseflies; it spreads mainly through infected blood, body fluids, sexual contact, and from mother to child. Therefore, the exception is Hepatitis B.
Why should glasswares be placed on a heat-resistant surface during heating?
A)
Prevent thermal shock
B)
Speeding up the process
C)
Save energy
D)
Increase efficiency
Glassware should be placed on a heat-resistant surface during heating to prevent sudden temperature changes that can crack or shatter the glass due to thermal shock. Heat-resistant surfaces distribute heat more safely and reduce stress on the glass. Options (b), (c), and (d) are incorrect because the main purpose is safety and protection of the glassware, not speeding up the process, saving energy, or increasing efficiency.
Sterilization of glassware is done by :
A)
Autoclave
B)
Phenolic compunds
C)
Tyndallization
D)
Hot air oven
Glassware is sterilized by dry heat, and the standard method is a hot air oven. Dry heat effectively sterilizes glass items such as Petri dishes, pipettes, test tubes, and flasks without causing rust or moisture-related problems.
Why others are incorrect:
- Autoclave: Uses moist heat under pressure; mainly for culture media, dressings, and some instruments, not the preferred standard method for glassware.
- Phenolic compounds: These are disinfectants, not a sterilization method for glassware.
- Tyndallization: A method of intermittent steaming used for certain heat-sensitive materials, not routine glassware sterilization.
Therefore, the correct answer is Hot air oven.
Wasserman Test for Syphilis is a type of:
A)
Agglutination test
B)
Precipitation test
C)
Neutralization test
D)
Complement fixation test
The Wassermann test is a classical serological test used for detecting syphilis, and it is based on the principle of complement fixation. In this test, if antibodies against the syphilis organism are present in the patient's serum, they react with the antigen and fix the complement. Therefore, the correct answer is (d) Complement fixation test.
Why others are incorrect:
(a) Agglutination test: involves clumping of particles or cells, not the basis of the Wassermann test.
(b) Precipitation test: involves formation of an insoluble antigen-antibody complex, not used here.
(c) Neutralization test: measures the ability of antibodies to neutralize toxins or viruses, not syphilis diagnosis in the Wassermann test.
Taxonomic classification of living beings into 5 kingdoms was developed by
A)
Hackel
B)
Chatton
C)
Copeland
D)
Whittaker
The five-kingdom classification system was proposed by R. H. Whittaker in 1969. He divided living organisms into Monera, Protista, Fungi, Plantae, and Animalia based on cell structure, body organization, mode of nutrition, reproduction, and phylogenetic relationships. Hence, option (d) is correct. The other options are incorrect because Haeckel proposed a three-kingdom system, Chatton distinguished prokaryotes and eukaryotes, and Copeland proposed a four-kingdom classification.