In the insect gut, the Bt toxin protein is converted from an inactive protoxin to its active form due to the:

[Biotechnology-and-its-Applications] [class-xii ]

• Presence of specific receptors on the surface of midgut cells.
• Highly acidic environment of the gut.
• Alkaline pH of the gut.
• Action of digestive enzymes.
Correct Option: C  [ Alkaline pH of the gut. ]

Remark: The Bt toxin protein exists as an inactive protoxin, but once ingested by an insect, it is converted into an active form due to the alkaline pH of the gut, which solubilizes the protein crystals.

Which specific Bt toxin gene controls the corn borer?

[Biotechnology-and-its-Applications] [class-xii ]

• cryIAc
• cryIAb
• cryIIAb
• cryIIAc
Correct Option: B  [ cryIAb ]

Remark: The proteins encoded by the genes cryIAc and cryIIAb control the cotton bollworms, while the gene cryIAb controls the corn borer.

RNA interference (RNAi) acts as a method of cellular defense in all eukaryotic organisms by causing the silencing of a specific mRNA due to a complementary:

[Biotechnology-and-its-Applications] [class-xii ]

• Single-stranded DNA molecule.
• Double-stranded RNA (dsRNA) molecule.
• Transfer RNA (tRNA) molecule.
• Ribosomal RNA (rRNA) molecule.
Correct Option: B  [ Double-stranded RNA (dsRNA) molecule. ]

Remark: RNA interference (RNAi) involves the silencing of a specific mRNA because a complementary double-stranded RNA (dsRNA) molecule binds to it, preventing its translation.

In the transgenic host plant designed to resist the nematode Meloidegyne incognitia, how was the necessary double-stranded RNA (dsRNA) generated?

[Biotechnology-and-its-Applications] [class-xii ]

• It was absorbed from the soil by the roots.
• It was introduced directly using a micro-injection.
• The introduced DNA produced both sense and anti-sense RNA.
• The Agrobacterium vector itself contained the dsRNA.
Correct Option: C  [ The introduced DNA produced both sense and anti-sense RNA. ]

Remark: Nematode-specific genes were introduced via Agrobacterium vectors such that the introduction of DNA produced both sense and anti-sense RNA in the host cells. These complementary RNAs formed a dsRNA, initiating RNAi.

A major advantage of recombinant therapeutics over similar products isolated from non-human sources is that they:

[Biotechnology-and-its-Applications] [class-xii ]

• Are easily synthesized by chemical reactions.
• Do not elicit unwanted immunological responses.
• Are generally cheaper to produce on a small scale.
• Require less downstream processing.
Correct Option: B  [ Do not elicit unwanted immunological responses. ]

Remark: Recombinant therapeutics do not induce unwanted immunological responses, which is common in products isolated from non-human sources (like animal insulin). They are also free from the risk of infection.

How many recombinant therapeutics approved for human use worldwide are currently marketed in India?

[Biotechnology-and-its-Applications] [class-xii ]

• 30
• 12
• 10
• 4
Correct Option: B  [ 12 ]

Remark: At present, about 30 recombinant therapeutics have been approved for human use worldwide. In India, 12 of these are presently being marketed.

Mature insulin consists of two short polypeptide chains, Chain A and Chain B, linked together by:

[Biotechnology-and-its-Applications] [class-xii ]

• Hydrogen bonds
• Peptide bonds
• C peptide bridge
• Disulphide bridges
Correct Option: D  [ Disulphide bridges ]

Remark: Insulin consists of two short polypeptide chains: Chain A and Chain B, that are linked together by disulphide bridges.

Insulin is synthesized in mammals as a pro-hormone. What is the extra stretch that needs to be removed for it to become a mature and functional hormone?

[Biotechnology-and-its-Applications] [class-xii ]

• A chain
• B chain
• C peptide
• Disulphide bridge
Correct Option: C  [ C peptide ]

Remark: Insulin is synthesized as a pro-hormone, which contains an extra stretch called the C peptide. This C peptide is removed during maturation into functional insulin.

What is the primary goal of Gene Therapy?

[Biotechnology-and-its-Applications] [class-xii ]

• To insert genes into a person’s cells and tissues to treat a disease by correcting a gene defect.
• To create hybrid organisms with desired traits.
• To produce diagnostic kits for early detection of pathogens.
• To synthesize non-human derived therapeutic proteins.
Correct Option: A  [ To insert genes into a person’s cells and tissues to treat a disease by correcting a gene defect. ]

Remark: Gene therapy is a collection of methods allowing correction of a gene defect diagnosed in a child/embryo. It involves inserting genes into a person’s cells and tissues to treat a disease by delivering a normal gene to compensate for the non-functional one.

If the ADA gene isolated from marrow cells is introduced into cells at early embryonic stages, the treatment for ADA deficiency could potentially be:

[Biotechnology-and-its-Applications] [class-xii ]

• Temporary, requiring periodic infusions.
• A permanent cure.
• Limited to enzyme replacement therapy.
• Cured only by bone marrow transplantation.
Correct Option: B  [ A permanent cure. ]

Remark: While current gene therapy for ADA requires periodic infusion of genetically engineered lymphocytes, if the gene is introduced into cells at early embryonic stages, it could be a permanent cure.