If a plasmid contains a selectable marker but lacks an *ori* sequence, what would be the result after transformation into the host?

[Biotechnology-Principles-and-Processes] [class-xii ]

• The plasmid would integrate into the host genome
• The plasmid would be maintained in high copy numbers
• The plasmid would be unable to replicate independently
• The host cell would become competent
Correct Option: C  [ The plasmid would be unable to replicate independently ]

Remark: The origin of replication is responsible for initiating replication; without it, the alien DNA cannot multiply itself.

The DNA polymerase enzyme used in PCR is thermostable, which means it remains active during the high temperature needed for:

[Biotechnology-Principles-and-Processes] [class-xii ]

• Primer annealing
• Hydrogen bonding
• Denaturation
• Ligation
Correct Option: C  [ Denaturation ]

Remark: The thermostable DNA polymerase remains active during the high temperature induced denaturation of double stranded DNA.

Which feature distinguishes a simple stirred-tank bioreactor from a shake flask?

[Biotechnology-Principles-and-Processes] [class-xii ]

• Presence of nutrient medium
• Ability to grow microorganisms
• Curved base and agitator system for control and aeration
• Sterile ambience
Correct Option: C  [ Curved base and agitator system for control and aeration ]

Remark: Stirred tank bioreactors have agitator and oxygen delivery systems, which provide better aeration and mixing than shake flasks.

The purpose of the enzyme *lysozyme* in the initial steps of RDT is to:

[Biotechnology-Principles-and-Processes] [class-xii ]

• Digest RNA molecules
• Degrade proteins
• Break the bacterial cell wall
• Join DNA fragments
Correct Option: C  [ Break the bacterial cell wall ]

Remark: Lysozyme is used to treat bacterial cells to break the cell open and release DNA.

Why are single recognition sites for restriction enzymes preferred in a cloning vector?

[Biotechnology-Principles-and-Processes] [class-xii ]

• To ensure blunt end formation
• To prevent fragmentation of the vector into multiple pieces
• To increase the speed of ligation
• To control the copy number
Correct Option: B  [ To prevent fragmentation of the vector into multiple pieces ]

Remark: Presence of more than one recognition site within the vector will generate several fragments, which will complicate the gene cloning.

If a non-recombinant plasmid is used in chromogenic selection, why do the colonies turn blue?

[Biotechnology-Principles-and-Processes] [class-xii ]

• The plasmid expresses the antibiotic resistance gene
• The inserted DNA activates the $\beta$-galactosidase gene
• The intact $\beta$-galactosidase gene breaks down the chromogenic substrate
• The host cell is naturally blue
Correct Option: C  [ The intact $\beta$-galactosidase gene breaks down the chromogenic substrate ]

Remark: If the plasmid does not have an insert (non-recombinant), the gene for $\beta$-galactosidase is intact, and its enzyme breaks down the chromogenic substrate to produce blue colour.

Which element is required in addition to an agitator system, oxygen delivery system, foam control system, and temperature control system in a bioreactor?

[Biotechnology-Principles-and-Processes] [class-xii ]

• UV sterilizer
• Sampling ports
• Micro-injection apparatus
• Ethidium bromide reservoir
Correct Option: B  [ Sampling ports ]

Remark: A bioreactor includes sampling ports so that small volumes of the culture can be withdrawn periodically.

The use of "disarmed pathogen" vectors is a method specifically for introducing alien DNA into:

[Biotechnology-Principles-and-Processes] [class-xii ]

• Bacterial cells only
• Yeast cells only
• Host cells (plant or animal)
• Fungal cells only
Correct Option: C  [ Host cells (plant or animal) ]

Remark: Disarmed pathogens (like modified Ti plasmid or retroviruses) are used to infect and transfer recombinant DNA into eukaryotic hosts (plant or animal cells).

Before restriction enzyme digestion, the DNA must be in pure form, which means it must be free from other macromolecules. Which enzyme is used to remove histone proteins from the DNA preparation?

[Biotechnology-Principles-and-Processes] [class-xii ]

• Ribonuclease
• Cellulase
• Protease
• Chitinase
Correct Option: C  [ Protease ]

Remark: Proteins (including histones) can be removed by treatment with protease.

Why is the maintenance of sterile ambience (bioprocess engineering) critical for the manufacture of biotechnological products?

[Biotechnology-Principles-and-Processes] [class-xii ]

• To ensure DNA does not denature
• To prevent competition and contamination by undesired microbes
• To increase the efficiency of DNA ligase
• To keep the temperature optimal
Correct Option: B  [ To prevent competition and contamination by undesired microbes ]

Remark: Bioprocess engineering is the maintenance of sterile (microbial contamination-free) ambience to enable growth of only the desired microbe.