Assertion (A):
The Polymerase Chain Reaction (PCR) requires the use of a thermostable DNA polymerase.
Reason (R):
The thermostable enzyme is required because it remains active and resists inactivation during the high temperature induced denaturation steps of the PCR cycles.

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

• (A) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion
• (B) Both Assertion and Reason are true, but Reason is not the correct explanation of Assertion
• (C) Assertion is true but Reason is false
• (D) Assertion is false but Reason is true
Correct Option: A  [ A ]

Remark: A is True: PCR uses a thermostable DNA polymerase.
R is True: The high temperature denaturation steps require an enzyme that remains active, which is why thermostable polymerase is used. R explains A.

Assertion (A):
Bioprocess engineering requires the maintenance of a sterile ambience in chemical engineering processes.
Reason (R):
Sterility ensures the growth of only the desired microbe or eukaryotic cell in large quantities for the manufacture of biotechnological products.

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

• (A) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion
• (B) Both Assertion and Reason are true, but Reason is not the correct explanation of Assertion
• (C) Assertion is true but Reason is false
• (D) Assertion is false but Reason is true
Correct Option: A  [ A ]

Remark: A is True: Bioprocess engineering involves maintaining a sterile environment (microbial contamination-free).
R is True: The purpose of maintaining sterility is specifically to allow only the desired organism to grow and produce the product. R explains A.

Assertion (A):
Small volume cultures cannot yield appreciable quantities of desired protein products.
Reason (R):
Bioreactors are large vessels (100–1000 litres) used to biologically convert raw materials into specific products using microbial, plant, animal, or human cells.

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

• (A) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion
• (B) Both Assertion and Reason are true, but Reason is not the correct explanation of Assertion
• (C) Assertion is true but Reason is false
• (D) Assertion is false but Reason is true
Correct Option: A  [ A ]

Remark: A is True: Small cultures are insufficient for large-scale production.
R is True: Bioreactors were developed to handle large volumes and optimize conditions for high yield. R describes the solution (Bioreactors) to the problem stated in A.

Assertion (A):
DNA fragments are separated in gel electrophoresis based on their size through the sieving effect of the agarose gel.
Reason (R):
DNA fragments, being negatively charged molecules, move towards the anode (positive electrode) under an electric field.

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

• (A) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion
• (B) Both Assertion and Reason are true, but Reason is not the correct explanation of Assertion
• (C) Assertion is true but Reason is false
• (D) Assertion is false but Reason is true
Correct Option: B  [ B ]

Remark: A is True: DNA fragments resolve (separate) according to size, where smaller fragments move farther.
R is True: DNA is negatively charged and moves toward the anode. R describes the *direction* of movement, which is necessary for separation (A), but A describes the *mechanism of separation* (sieving by size). R does not explain A.

Assertion (A):
In gel electrophoresis, separated DNA fragments can only be visualized after staining the gel with ethidium bromide and exposure to UV radiation.
Reason (R):
Pure DNA fragments are not visible in visible light without staining.

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

• (A) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion
• (B) Both Assertion and Reason are true, but Reason is not the correct explanation of Assertion
• (C) Assertion is true but Reason is false
• (D) Assertion is false but Reason is true
Correct Option: A  [ A ]

Remark: A is True: This is the standard procedure for visualizing DNA bands.
R is True: The necessity of the procedure (A) stems directly from the fact that DNA is invisible under visible light without staining. R explains A.

Assertion (A):
The DNA that precipitates out after appropriate treatment and addition of chilled ethanol can be seen as a collection of fine threads in the suspension.
Reason (R):
This precipitated DNA is removed from the suspension by a process called spooling.

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

• (A) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion
• (B) Both Assertion and Reason are true, but Reason is not the correct explanation of Assertion
• (C) Assertion is true but Reason is false
• (D) Assertion is false but Reason is true
Correct Option: B  [ B ]

Remark: A is True: Purified DNA precipitates in chilled ethanol as fine threads.
R is True: The technique used to collect this DNA is called spooling. R describes the subsequent step after A, but does not explain why the DNA appears as fine threads or why it precipitates in ethanol.

Assertion (A):
The techniques of genetic engineering overcome the limitations of traditional hybridisation by allowing scientists to introduce only a specific set of desirable genes.
Reason (R):
Traditional hybridisation often leads to the inclusion and multiplication of undesirable genes along with the desired ones.

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

• (A) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion
• (B) Both Assertion and Reason are true, but Reason is not the correct explanation of Assertion
• (C) Assertion is true but Reason is false
• (D) Assertion is false but Reason is true
Correct Option: A  [ A ]

Remark: A is True: Genetic engineering allows the introduction of only specific desirable genes.
R is True: Traditional methods suffer from introducing undesirable genes. R describes the flaw that genetic engineering (A) was developed to fix, thus R explains A.

Assertion (A):
Micro-injection is the method typically used for introducing recombinant DNA directly into the nucleus of a plant cell.
Reason (R):
Biolistics (gene gun) method, which uses high velocity micro-particles, is a suitable method for animal cells.

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

• (A) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion
• (B) Both Assertion and Reason are true, but Reason is not the correct explanation of Assertion
• (C) Assertion is true but Reason is false
• (D) Assertion is false but Reason is true
Correct Option: D  [ D ]

Remark: A is False: Micro-injection is used for introducing recombinant DNA into the nucleus of an *animal* cell.
R is True: The biolistics method, or gene gun, which bombards cells with micro-particles, is generally suitable for *plants*.

Assertion (A):
For large-scale production, continuous culture systems are used wherein fresh medium is added while used medium is drained out from the other side.
Reason (R):
Continuous culture maintains the cells in their physiologically most active log/exponential phase, leading to higher yields of the desired protein.

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

• (A) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion
• (B) Both Assertion and Reason are true, but Reason is not the correct explanation of Assertion
• (C) Assertion is true but Reason is false
• (D) Assertion is false but Reason is true
Correct Option: A  [ A ]

Remark: A is True: Continuous culture involves draining used medium and adding fresh medium.
R is True: This specific type of culturing method is used because it keeps cells in the log/exponential phase, resulting in larger biomass and higher yields. R explains A.

Assertion (A):
The Ti plasmid of Agrobacterium tumifaciens has been modified into a cloning vector for gene delivery into a variety of plants.
Reason (R):
Scientists derived knowledge for generating useful vectors by observing how pathogens like Agrobacterium and retroviruses deliver genes to transform eukaryotic cells.

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

• (A) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion
• (B) Both Assertion and Reason are true, but Reason is not the correct explanation of Assertion
• (C) Assertion is true but Reason is false
• (D) Assertion is false but Reason is true
Correct Option: A  [ A ]

Remark: A is True: The tumor inducing (Ti) plasmid has been modified to be non-pathogenic yet capable of delivering genes to plants.
R is True: Knowledge about gene delivery by pathogens (like Agrobacterium in plants) provided the basis for developing these vectors. R explains the fundamental knowledge that led to the development described in A.