Free Mock Test 2026
Free NEET Biotechnology Principles and Processes Important MCQs Practice Test — Practice Questions
1. In agarose gel electrophoresis, DNA fragments move toward the:
- (A) Cathode, because DNA is positively charged
- (B) Anode, because DNA is negatively charged
- (C) Cathode, because DNA is negatively charged
- (D) Neither electrode
Answer: (B) Anode, because DNA is negatively charged
DNA is negatively charged, so it moves to the positive electrode. Smaller fragments move farther.
2. Purified DNA appears as fine threads in the solution when:
- (A) Protease is added
- (B) The solution is heated
- (C) It is treated with RNase
- (D) Chilled ethanol is added
Answer: (D) Chilled ethanol is added
DNA precipitates in chilled ethanol and can be spooled out as fine threads.
3. DNA bands in an agarose gel are visualised by staining with ethidium bromide and exposing the gel to:
- (A) UV radiation
- (B) Infrared radiation
- (C) Visible light only
- (D) X-rays
Answer: (A) UV radiation
Ethidium bromide-stained DNA shows bright orange bands under UV light.
4. Which enzyme is used to remove RNA when isolating DNA?
- (A) Protease
- (B) Lipase
- (C) Ribonuclease
- (D) Cellulase
Answer: (C) Ribonuclease
Ribonuclease degrades RNA. Protease removes proteins.
5. Foreign DNA is inserted at the BamHI site within the tetracycline resistance gene of pBR322. The transformed bacteria will be:
- (A) Sensitive to both ampicillin and tetracycline
- (B) Resistant to tetracycline and sensitive to ampicillin
- (C) Resistant to both
- (D) Resistant to ampicillin and sensitive to tetracycline
Answer: (D) Resistant to ampicillin and sensitive to tetracycline
Insertion inactivates tetR, so the recombinants lose tetracycline resistance but keep ampicillin resistance.
6. Bacterial cells are made competent to take up recombinant DNA by treating them with:
- (A) Ethidium bromide
- (B) Divalent cations such as calcium, followed by a heat shock
- (C) Lysozyme only
- (D) A high concentration of ethanol
Answer: (B) Divalent cations such as calcium, followed by a heat shock
Calcium ions increase the efficiency of DNA entry through the cell wall pores, and a brief heat shock (42°C) helps the DNA enter.
7. Sticky ends are useful in cloning because they:
- (A) Are cut by DNA ligase
- (B) Are blunt and fit any DNA
- (C) Prevent DNA from replicating
- (D) Form hydrogen bonds with complementary sticky ends of another fragment cut by the same enzyme
Answer: (D) Form hydrogen bonds with complementary sticky ends of another fragment cut by the same enzyme
Complementary sticky ends base-pair easily, and DNA ligase then seals the joint.
8. The DNA polymerase used in PCR is isolated from:
- (A) E. coli
- (B) Bacillus thuringiensis
- (C) Thermus aquaticus
- (D) Agrobacterium tumefaciens
Answer: (C) Thermus aquaticus
Taq polymerase comes from the thermophilic bacterium Thermus aquaticus and stays active at the high temperature of denaturation.
9. Exonucleases differ from endonucleases in that exonucleases:
- (A) Cut DNA at specific internal sites
- (B) Remove nucleotides from the ends of DNA
- (C) Join DNA fragments
- (D) Synthesise primers
Answer: (B) Remove nucleotides from the ends of DNA
Exonucleases remove nucleotides from the ends, while restriction endonucleases cut at specific positions within the DNA.
10. Which enzyme is used to break the cell wall of fungal cells during DNA isolation?
- (A) Chitinase
- (B) Cellulase
- (C) Lysozyme
- (D) Ribonuclease
Answer: (A) Chitinase
Fungal cell walls contain chitin. Cellulase is used for plant cells and lysozyme for bacteria.
11. In the vector pBR322, the genes ampR and tetR are used as:
- (A) Origins of replication
- (B) Recognition sites
- (C) Selectable markers
- (D) Promoters
Answer: (C) Selectable markers
These antibiotic resistance genes help to identify and eliminate non-transformants.
12. The 'ori' sequence in a cloning vector is responsible for:
- (A) Initiating replication and controlling the copy number of the linked DNA
- (B) Selecting transformants
- (C) Cutting DNA
- (D) Recognising restriction sites
Answer: (A) Initiating replication and controlling the copy number of the linked DNA
Origin of replication is the sequence from which replication starts. It also decides the copy number.
13. The correct sequence of steps in one PCR cycle is:
- (A) Extension, annealing, denaturation
- (B) Annealing, denaturation, extension
- (C) Denaturation, extension, annealing
- (D) Denaturation, annealing, extension
Answer: (D) Denaturation, annealing, extension
DNA is denatured by heat, primers anneal to the single strands, and Taq polymerase extends them.
14. EcoRI cuts DNA between which two bases of its recognition sequence 5′-GAATTC-3′?
- (A) A and T
- (B) T and C
- (C) G and A
- (D) A and A
Answer: (C) G and A
EcoRI cuts between G and A on both strands, leaving single-stranded overhangs called sticky ends.
15. In the name EcoRI, the letter R represents the:
- (A) Strain of the bacterium
- (B) Genus of the bacterium
- (C) Species of the bacterium
- (D) Order in which the enzyme was isolated
Answer: (A) Strain of the bacterium
Eco comes from Escherichia coli, R from the strain RY13, and I from the order of isolation.
16. A palindromic nucleotide sequence in DNA is one that:
- (A) Contains only purines
- (B) Reads the same on both strands when read in the 5′→3′ direction
- (C) Is found only in plasmids
- (D) Has equal numbers of A and G
Answer: (B) Reads the same on both strands when read in the 5′→3′ direction
The sequence on the two strands is the same when each is read 5′→3′. Restriction enzymes recognise such sequences.
17. In 1972, Stanley Cohen and Herbert Boyer constructed the first recombinant DNA by linking an antibiotic resistance gene with the native plasmid of:
- (A) E. coli
- (B) Agrobacterium tumefaciens
- (C) Bacillus thuringiensis
- (D) Salmonella typhimurium
Answer: (D) Salmonella typhimurium
They isolated an antibiotic resistance gene from Salmonella typhimurium and linked it with a plasmid vector.
18. Downstream processing refers to:
- (A) Insertion of the gene into the host
- (B) Growth of the host in the bioreactor
- (C) Separation and purification of the product, followed by quality control tests, before marketing
- (D) Selection of transformed colonies
Answer: (C) Separation and purification of the product, followed by quality control tests, before marketing
The product is separated, purified, formulated with preservatives and tested before it is sold.
19. Stirred-tank bioreactors are preferred over shake flasks for large-scale production because they:
- (A) Provide better mixing, oxygen supply and control of pH and temperature
- (B) Do not need sterile conditions
- (C) Avoid downstream processing
- (D) Work only for anaerobic microbes
Answer: (A) Provide better mixing, oxygen supply and control of pH and temperature
A stirrer and sparger give uniform mixing and oxygen, and sensors control the conditions.
20. In PCR, primers are:
- (A) Long double-stranded DNA fragments
- (B) Short chemically synthesised oligonucleotides complementary to regions of the template DNA
- (C) Enzymes that extend DNA
- (D) Subunits of RNA polymerase
Answer: (B) Short chemically synthesised oligonucleotides complementary to regions of the template DNA
Two sets of primers anneal to the ends of the target region and give the polymerase a starting point.