Why does the Bt toxin protein, produced by Bacillus thuringiensis, not typically kill the bacterium itself?

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

• The bacteria are resistant to the toxin.
• The toxin exists as an inactive protoxin.
• The toxin is enclosed in a special sac within the bacterium.
• The bacteria possess a neutralizing enzyme.
Correct Option: B  [ The toxin exists as an inactive protoxin. ]

Remark: The Bt toxin protein exists as an inactive protoxin. It only becomes converted into an active form due to the alkaline pH of the insect gut which solubilizes the crystals, causing cell swelling and lysis [1-3].

Which American company prepared the A and B chains of human insulin separately in 1983 and combined them using disulfide bonds?

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

• Bayer
• Biogen
• Eli Lilly
• Genentech
Correct Option: C  [ Eli Lilly ]

Remark: In 1983, Eli Lilly, an American company, prepared two DNA sequences corresponding to the A and B chains of human insulin. These sequences were introduced into plasmids of E. coli to produce the chains separately, which were then extracted and combined by creating disulfide bonds to form human insulin [4, 5].

The novel strategy used to protect tobacco plants from infestation by the nematode Meloidegyne incognitia was based on which molecular mechanism?

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

• Somatic hybridization
• Micro-propagation
• RNA interference (RNAi)
• Enzyme Linked Immuno-sorbent Assay (ELISA)
Correct Option: C  [ RNA interference (RNAi) ]

Remark: The strategy utilized RNA interference (RNAi), a method of cellular defense involving the silencing of a specific mRNA due to a complementary double-stranded RNA (dsRNA) molecule. Nematode-specific genes were introduced into the host plant via Agrobacterium vectors, generating dsRNA that silenced the parasite’s specific mRNA, protecting the transgenic host [6-8].

The first clinical gene therapy was given in 1990 for the treatment of which specific deficiency?

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

• Cancer
• Cystic Fibrosis
• Adenosine Deaminase (ADA) deficiency
• Rheumatoid arthritis
Correct Option: C  [ Adenosine Deaminase (ADA) deficiency ]

Remark: The first clinical gene therapy was provided in 1990 to a 4-year-old girl with adenosine deaminase (ADA) deficiency, a disorder caused by the deletion of the gene for this enzyme crucial for the immune system [9].

What human protein was present in the milk produced by Rosie, the first transgenic cow, making it nutritionally superior for human babies?

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

• Pro-insulin
• Alpha-1-antitrypsin
• Human alpha-lactalbumin
• Human growth factor
Correct Option: C  [ Human alpha-lactalbumin ]

Remark: Rosie, the first transgenic cow (produced in 1997), produced human protein-enriched milk (2.4 grams per litre). This milk contained the human alpha-lactalbumin and was considered nutritionally a more balanced product for human babies than natural cow-milk [10].

Which of the following is NOT listed as one of the three critical research areas of biotechnology?

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

• Providing the best catalyst in the form of an improved organism or pure enzyme.
• Creating optimal conditions through engineering for a catalyst to act.
• Downstream processing technologies to purify the protein/organic compound.
• Development of new conventional breeding techniques for crop improvement.
Correct Option: D  [ Development of new conventional breeding techniques for crop improvement. ]

Remark: The three critical research areas of biotechnology are: (i) Providing the best catalyst (usually a microbe or pure enzyme), (ii) Creating optimal conditions through engineering for the catalyst to act, and (iii) Downstream processing technologies to purify the protein/organic compound [1, 2]. Conventional breeding techniques are mentioned as failing to keep pace with demand, necessitating new technologies like tissue culture [3].

The capacity of a plant part (explant) to regenerate a whole plant from any cell is known as:

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

• Micro-propagation
• Somatic hybridisation
• Somaclonal variation
• Totipotency
Correct Option: D  [ Totipotency ]

Remark: The capacity to generate a whole plant from any cell or explant is called totipotency [4]. The explant is any part of a plant taken out and grown in a test tube under sterile conditions in special nutrient media [3, 4].

Genetically Modified (GM) plants offer several advantages. Golden rice specifically enhanced the nutritional value of food by being enriched with:

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

• Iron and Zinc
• Proteins
• Vitamin A
• Vitamin B12
Correct Option: C  [ Vitamin A ]

Remark: Genetic modification has enhanced the nutritional value of food, exemplified by golden rice, which is Vitamin A enriched rice [5].

The specific Bt toxin genes that control the cotton bollworms are:

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

• cryIAb and cryIAc
• cryIAb and cryIIAb
• cryIAc and cryIIAb
• cryIIAb and cryIAd
Correct Option: C  [ cryIAc and cryIIAb ]

Remark: Bt toxins are insect-group specific. The proteins encoded by the genes cryIAc and cryIIAb control the cotton bollworms, while the gene cryIAb controls corn borer [6]. The toxin is coded by a gene named cry [6].

The strategy used to prevent infestation of tobacco plant roots by the nematode Meloidegyne incognitia was based on which molecular mechanism?

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

• Somatic hybridization
• DNA amplification using PCR
• RNA interference (RNAi)
• Enzyme Linked Immuno-sorbent Assay (ELISA)
Correct Option: C  [ RNA interference (RNAi) ]

Remark: A novel strategy based on RNA interference (RNAi) was adopted to prevent infestation by the nematode Meloidegyne incognitia, which infects the roots of tobacco plants and reduces yield [6, 7]. This method involves the silencing of a specific mRNA due to a complementary double-stranded RNA (dsRNA) molecule [7].