In molecular diagnosis utilizing a probe and autoradiography, what is the probe typically tagged with?

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

• An enzyme that produces color.
• A specific antibiotic.
• A fluorescent dye.
• A radioactive molecule.
Correct Option: D  [ A radioactive molecule. ]

Remark: A single stranded DNA or RNA, tagged with a radioactive molecule (probe) is allowed to hybridise to its complementary DNA in a clone of cells.

If a clone contains a mutated gene during molecular diagnosis using a radioactive probe and autoradiography, what is the resulting observation?

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

• The probe will show strong binding and fluorescence.
• The gene will be amplified significantly.
• The clone will not appear on the photographic film.
• The clone will immediately undergo lysis.
Correct Option: C  [ The clone will not appear on the photographic film. ]

Remark: If the gene is mutated, the radioactive probe will not have complementarity, and consequently, the clone having the mutated gene will not appear on the photographic film after autoradiography.

What type of vector was used in the first clinical gene therapy for ADA deficiency to introduce the functional ADA cDNA into the lymphocytes?

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

• Agrobacterium vector
• Plasmid vector
• Retroviral vector
• Cosmid vector
Correct Option: C  [ Retroviral vector ]

Remark: As a first step towards gene therapy for ADA deficiency, a functional ADA cDNA (using a retroviral vector) is introduced into lymphocytes grown outside the body.

Bone marrow transplantation and enzyme replacement therapy are listed as treatments for ADA deficiency, but both approaches suffer from the drawback that they are:

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

• Extremely painful.
• Not completely curative.
• Limited to patients over 10 years old.
• Highly prone to viral infection.
Correct Option: B  [ Not completely curative. ]

Remark: Bone marrow transplantation and enzyme replacement therapy, while used to treat ADA deficiency, are problematic because they are not completely curative.

Recombinant therapeutics are considered superior to similar products isolated from non-human sources because they are free from the risk of infection and do not induce:

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

• High production costs.
• Rapid degradation.
• Unwanted immunological responses.
• Need for purification (downstream processing).
Correct Option: C  [ Unwanted immunological responses. ]

Remark: The recombinant therapeutics do not induce unwanted immunological responses as is common in case of similar products isolated from non-human sources, and are also free from the risk of infection.

What is the fundamental principle behind the diagnostic technique ELISA (Enzyme Linked Immuno-sorbent Assay)?

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

• Gene amplification using thermocyclers.
• Hybridization of nucleic acids with radioactive probes.
• Antigen-antibody interaction.
• Protoplast fusion and culture.
Correct Option: C  [ Antigen-antibody interaction. ]

Remark: ELISA is based on the principle of antigen-antibody interaction. It detects infection by identifying the presence of antigens (proteins, glycoproteins) or by detecting antibodies synthesized against the pathogen.

Which type of molecule, when tagged with a radioactive molecule (probe), is used in molecular diagnosis followed by detection using autoradiography?

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

• A double-stranded DNA or RNA molecule.
• A single-stranded DNA or RNA molecule.
• A ribosomal RNA (rRNA) molecule.
• A transfer RNA (tRNA) molecule.
Correct Option: B  [ A single-stranded DNA or RNA molecule. ]

Remark: A single stranded DNA or RNA, tagged with a radioactive molecule (probe) is allowed to hybridise to its complementary DNA in a clone of cells.

In the context of Bt toxin, what is the role of the alkaline pH in the insect gut?

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

• It neutralizes the toxin, protecting the insect.
• It solubilizes the inactive protoxin crystals, converting them to the active form.
• It promotes the synthesis of new toxin molecules.
• It destroys the cell receptors necessary for toxin binding.
Correct Option: B  [ It solubilizes the inactive protoxin crystals, converting them to the active form. ]

Remark: The Bt toxin protein exists as an inactive protoxin. Once ingested, the alkaline pH of the gut solubilizes the crystals, converting the protoxin into the active form of the toxin.

After activation, where does the Bt toxin bind within the insect body to initiate cell death?

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

• The surface of midgut epithelial cells.
• The chitin layer of the exoskeleton.
• The nuclei of muscle cells.
• The membranes of brain cells.
Correct Option: A  [ The surface of midgut epithelial cells. ]

Remark: The activated Bt toxin binds to the surface of midgut epithelial cells, creating pores that cause cell swelling and lysis, leading to the death of the insect.

Besides Bt cotton, which of the following is listed as an example of a crop plant into which Bt toxin genes have been incorporated?

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

• Wheat
• Rice
• Barley
• Oats
Correct Option: B  [ Rice ]

Remark: Examples of crop plants where Bt toxin genes have been incorporated include Bt cotton, Bt corn, rice, tomato, potato and soyabean.