The thermostable DNA polymerase remains active during the high temperature step in PCR, which is required for:

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

• Annealing of primers
• Denaturation of double-stranded DNA
• Extension of primers
• Ligation of fragments
Correct Option: B  [ Denaturation of double-stranded DNA ]

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

If transformed *E. coli* cells (carrying ampicillin resistance) are spread on agar plates containing ampicillin, what happens to the untransformed recipient cells?

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

• They grow rapidly
• They die
• They remain dormant
• They become heat-sensitive
Correct Option: B  [ They die ]

Remark: Untransformed recipient cells will die because they lack the resistance gene.

The ampicillin resistance gene in a recombinant DNA molecule is referred to as a selectable marker because it allows the researcher to:

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

• Increase the copy number of the plasmid
• Cut the DNA at specific locations
• Select a transformed cell in the presence of ampicillin
• Purify the desired protein
Correct Option: C  [ Select a transformed cell in the presence of ampicillin ]

Remark: The ampicillin resistance gene is called a selectable marker because one is able to select a transformed cell in its presence.

If a protein encoding gene is expressed in a heterologous host (an alien host), the resulting protein is called a:

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

• Native protein
• Host protein
• Recombinant protein
• Mutated protein
Correct Option: C  [ Recombinant protein ]

Remark: If any protein encoding gene is expressed in a heterologous host, it is called a recombinant protein.

In a continuous culture system, cells are maintained in their physiologically most active phase to produce a larger biomass. This phase is the:

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

• Lag phase
• Stationary phase
• Decline phase
• Log/exponential phase
Correct Option: D  [ Log/exponential phase ]

Remark: Continuous culturing maintains cells in their physiologically most active log/exponential phase for higher yields of desired protein.

Bioreactors were developed to process large volumes of culture, typically between:

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

• 10-50 litres
• 50-100 litres
• 100-1000 litres
• 1000-5000 litres
Correct Option: C  [ 100-1000 litres ]

Remark: Bioreactors process large volumes (100-1000 litres) of culture.

A bioreactor provides optimal growth conditions by controlling temperature, pH, substrate, salts, vitamins, and:

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

• Pressure
• Gravity
• Oxygen
• UV light
Correct Option: C  [ Oxygen ]

Remark: Optimal growth conditions provided by a bioreactor include oxygen availability.

The most commonly used bioreactors are of the:

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

• Shaker type
• Stirring type
• Batch type
• Continuous type
Correct Option: B  [ Stirring type ]

Remark: The most commonly used bioreactors are of stirring type (simple or sparged).

What feature of a stirred-tank bioreactor facilitates even mixing and oxygen availability throughout the vessel?

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

• The temperature control system
• The curved base
• The agitator system (stirrer)
• The foam control system
Correct Option: C  [ The agitator system (stirrer) ]

Remark: The stirrer facilitates even mixing and oxygen availability throughout the bioreactor.

After the biosynthetic stage, the processes including separation and purification are collectively referred to as:

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

• Bioprocess engineering
• Upstream processing
• Downstream processing
• Quality control testing
Correct Option: C  [ Downstream processing ]

Remark: Separation and purification processes are collectively referred to as downstream processing.