Biotechnology: Principles and Processes

1. Rising of dough is due to:

a. Multiplication of yeast

b. Production of CO2

c. Emulsification

d. Hydrolysis of wheat flour starch into sugars.

Key Answer: b. Production of CO2

Explanation: Yeast releases carbon dioxide during fermentation. The gas causes the dough to rise and become soft.

2. Which of the following enzymes catalyse the removal of nucleotides from the ends of DNA?

a. endonuclease

b. exonuclease

c. DNA ligase

d. Hind - II

Key Answer: b. exonuclease

Explanation: Exonucleases remove nucleotides from DNA ends. They digest DNA in one direction from terminal ends.

3. The transfer of genetic material from one bacterium to another through the mediation of a viral vector is termed as:

a. Transduction

b. Conjugation

c. Transformation

d. Translation

Key Answer: a. Transduction

Explanation: Transduction occurs through bacteriophages acting as vectors. Viral particles transfer bacterial genes between cells.

4. Which of the given statements is correct in the context of visualizing DNA molecules separated by agarose gel electrophoresis?

a. DNA can be seen in visible light

b. DNA can be seen without staining in visible light

c. Ethidium bromide stained DNA can be seen in visible light

d. Ethidium bromide stained DNA can be seen under exposure to UV light

Key Answer: d. Ethidium bromide stained DNA can be seen under exposure to UV light

Explanation: Ethidium bromide intercalates with DNA and fluoresces under UV light. This allows DNA bands to become visible.

5. 'Restriction' in Restriction enzyme refers to:

a. Cleaving of phosphodiester bond in DNA by the enzyme

b. Cutting of DNA at specific position only

c. Prevention of the multiplication of bacteriophage by the host bacteria

d. All of the above

Key Answer: c. Prevention of the multiplication of bacteriophage by the host bacteria

Explanation: Restriction enzymes protect bacteria by cutting foreign phage DNA. This restricts bacteriophage multiplication.

6. Which of the following is not required in the preparation of a recombinant DNA molecule?

a. Restriction endonuclease

b. DNA ligase

c. DNA fragments

d. E.coli

Key Answer: d. E.coli

Explanation: Recombinant DNA formation requires enzymes and DNA fragments. E.coli is used later as a host organism.

7. In agarose gel electrophoresis, DNA molecules are separated on the basis of their:

a. Charge only

b. Size only

c. Charge to size ratio

d. All of the above

Key Answer: b. Size only

Explanation: DNA fragments move through agarose according to size. Smaller fragments migrate faster than larger ones.

8. The most important feature in a plasmid to serve as a vector in gene cloning experiment is:

a. Origin of replication (ori)

b. Presence of a selectable marker

c. Presence of sites for restriction endonuclease

d. Its size

Key Answer: a. Origin of replication (ori)

Explanation: Ori enables plasmid replication inside host cells. Without replication, cloned DNA cannot multiply.

9. While isolating DNA from bacteria, which of the following enzymes is not required?

a. Lysozyme

b. Ribonuclease

c. Deoxyribonuclease

d. Protease

Key Answer: c. Deoxyribonuclease

Explanation: Deoxyribonuclease degrades DNA and would destroy the sample. Other enzymes help remove contaminants.

10. Which of the following contributed in popularising the PCR (polymerase chain reactions) technique?

a. Easy availability of DNA template

b. Availability of synthetic primers

c. Availability of cheap deoxyribonucleotides

d. Availability of 'Thermostable' DNA polymerase

Key Answer: d. Availability of 'Thermostable' DNA polymerase

Explanation: Thermostable Taq polymerase withstands repeated heating cycles. This made PCR rapid and efficient.

11. An antibiotic resistance gene in a vector usually helps in the selection of:

a. Competent bacterial cells

b. Transformed bacterial cells

c. Recombinant bacterial cells

d. None of the above

Key Answer: b. Transformed bacterial cells

Explanation: Only bacteria carrying the vector survive in antibiotic medium. This helps identify transformed cells.

12. Significance of 'heat shock' method in bacterial transformation is to facilitate:

a. Binding of DNA to the cell wall

b. Uptake of DNA through membrane transport proteins

c. Uptake of DNA through transient pores in the bacterial cell wall

d. Expression of antibiotic resistance gene

Key Answer: c. Uptake of DNA through transient pores in the bacterial cell wall

Explanation: Heat shock creates temporary pores in bacterial membranes. Foreign DNA enters through these openings.

13. The role of DNA ligase in the construction of a recombinant DNA molecule is:

a. Formation of phosphodiester bond between two DNA fragments

b. Formation of hydrogen bonds between sticky ends of DNA fragments

c. Ligation of all purime and pyrimidine bases

d. None of the above

Key Answer: a. Formation of phosphodiester bond between two DNA fragments

Explanation: DNA ligase joins DNA fragments by sealing sugar-phosphate backbones. It forms stable phosphodiester bonds.

14. Which of the following bacteria is not a source of restriction endonuclease?

a. Haemophilus influenzae

b. Escherichia coli

c. Entamoeba coli

d. Bacillus amyloliquefaciens

Key Answer: c. Entamoeba coli

Explanation: Entamoeba coli is a protozoan, not a bacterium. Restriction enzymes are isolated from bacteria.

15. Which of the following steps are catalysed by Taq DNA polymerase in a PCR reaction?

a. Denaturation of template DNA

b. Annealing of primers to template DNA

c. Extension of primer end on the template DNA

d. All of the above

Key Answer: c. Extension of primer end on the template DNA

Explanation: Taq polymerase synthesizes new DNA strands from primers. Denaturation and annealing are temperature-driven processes.

16. A bacterial cell was transformed with a recombinant DNA molecule that was generated using a human gene. However, the transformed cells did not produce the desired protein. Reasons could be:

a. Human gene may have intron which bacteria cannot process

b. Amino acid codons for humans and bacteria are different

c. Human protein is formed but degraded by bacteria

d. All of the above

Key Answer: a. Human gene may have intron which bacteria cannot process

Explanation: Bacteria lack machinery for intron splicing. Hence many eukaryotic genes cannot be expressed directly.

17. Which of the following should be chosen for best yield if one were to produce a recombinant protein in large amounts?

a. Laboratory flask of largest capacity

b. A stirred-tank bioreactor without in-lets and out-lets

c. A continuous culture system

d. Any of the above

Key Answer: c. A continuous culture system

Explanation: Continuous culture maintains ideal growth conditions constantly. This ensures high yield of recombinant proteins.

18. Who among the following was awarded the Nobel Prize for the development of PCR technique?

a. Herbert Boyer

b. Hargovind Khurana

c. Kary Mullis

d. Arthur Kornberg

Key Answer: c. Kary Mullis

Explanation: Kary Mullis developed the PCR technique in 1983. PCR revolutionized molecular biology and diagnostics.

19. Which of the following statements does not hold true for restriction enzyme?

a. It recognises a palindromic nucleotide sequence

b. It is an endonuclease

c. It is isolated from viruses

d. It can produce the same kind of sticky ends in different DNA molecules

Key Answer: c. It is isolated from viruses

Explanation: Restriction enzymes are isolated from bacteria, not viruses. They recognize specific palindromic DNA sequences.