Chapter 10: Biotechnology and its Applications Short Questions | biology Class 12 CBSE

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Chapter 10: Biotechnology and its Applications Short Questions | biology Class 12 CBSE | ByteNotes.in

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Question 1

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What is totipotency? How is it exploited in plant biotechnology?

Totipotency is the capacity of any plant cell or explant to regenerate into a complete organism when cultured under appropriate sterile conditions.
It is exploited in micropropagation, where explants are grown in nutrient media containing sucrose, inorganic salts, vitamins, amino acids, and growth regulators to produce thousands of somaclones.
This technique is used commercially for rapid propagation of important food plants like tomato, banana, and apple.

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Question 2

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Distinguish between somaclones and somatic hybrids.

Somaclones are plants produced by micropropagation that are genetically identical to the original parent plant from which they were grown.
Somatic hybrids are new plants formed by fusing protoplasts of two different plant varieties through somatic hybridisation, combining desirable characteristics of both parents.
While somaclones maintain genetic uniformity, somatic hybrids introduce genetic variation by combining two distinct genomes, exemplified by pomato (tomato + potato).

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Question 3

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Why is meristem used for obtaining virus-free plants in tissue culture?

Even when a plant is infected with a virus, the apical and axillary meristematic regions remain free of the virus.
The meristem is therefore excised and cultured in vitro under sterile conditions to obtain virus-free plantlets.
This technique has been successfully applied to crops such as banana, sugarcane, and potato to produce disease-free planting material.

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Question 4

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Why does Bt toxin not kill the Bacillus thuringiensis bacterium that produces it?

Bt toxin exists in an inactive form called protoxin inside the Bacillus cells, so it is not harmful to the bacterium itself.
The protoxin is activated only in the alkaline pH of the insect's midgut, where the crystals dissolve and the toxin becomes active.
Since the bacterium does not have an alkaline gut environment, the toxin remains inactive and does not cause any harm to the bacterial cells.

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Question 5

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Name the cry genes responsible for controlling cotton bollworm and corn borer. What do these genes encode?

The genes cryIAc and cryIIAb control cotton bollworm, while cryIAb controls the corn borer.
These genes encode Cry proteins (insecticidal crystal proteins), which are toxic insecticidal proteins that belong to the Bt toxin family.
The cry genes are cloned from Bacillus thuringiensis and incorporated into crop plants to confer insect resistance without the use of chemical insecticides.

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Question 6

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What is RNAi? Why is it described as a method of cellular defense?

RNA interference (RNAi) is a cellular mechanism in which a specific mRNA is silenced by a complementary double-stranded RNA (dsRNA) molecule that binds to and prevents its translation.
It is a method of cellular defense because it protects eukaryotic cells against viral RNA genomes and mobile genetic elements (transposons) that replicate via RNA intermediates.
The dsRNA triggers degradation or translational silencing of the complementary mRNA, preventing expression of foreign or unwanted genes.

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Question 7

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How was RNAi used to protect tobacco plants from the nematode Meloidogyne incognita?

Nematode-specific genes were introduced into tobacco plants using Agrobacterium vectors such that both sense and anti-sense RNA were produced in the host cells.
These complementary RNA molecules formed double-stranded RNA (dsRNA), which initiated RNAi and silenced the specific mRNA of the nematode.
As a result, the nematode could not survive in the transgenic host and the plant was protected from the parasite.

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Question 8

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State two advantages of recombinant therapeutics over products isolated from non-human sources.

Recombinant therapeutics are identical to human proteins, so they do not induce unwanted immunological responses such as allergic reactions.
They are free from the risk of infection that is associated with products isolated from non-human animal sources.
Recombinant DNA technology enables mass production of these drugs, making them more widely available and cost-effective.

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Question 9

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Why was the production of human insulin using recombinant DNA technology challenging?

In mammals, insulin is synthesised as a pro-hormone (pro-insulin) that contains an extra C peptide, which must be removed during maturation into a functional hormone.
The main challenge was getting the insulin chains assembled into a mature, functional form outside the normal cellular processing environment.
Eli Lilly solved this in 1983 by producing insulin chains A and B separately in E. coli and then combining them using disulfide bonds to form functional human insulin.

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Question 10

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What was the significance of the first clinical gene therapy in 1990?

The first clinical gene therapy was given to a 4-year-old girl with adenosine deaminase (ADA) deficiency, a hereditary disorder caused by deletion of the ADA gene.
It demonstrated that a functional ADA cDNA could be introduced into a patient's lymphocytes via a retroviral vector, allowing the cells to produce the missing enzyme.
This established proof-of-concept that gene therapy could treat hereditary diseases that could not be completely cured by conventional approaches like bone marrow transplantation or enzyme replacement therapy.

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Question 11

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Why must a patient who receives gene therapy for ADA deficiency undergo periodic infusions of engineered lymphocytes?

The lymphocytes into which the functional ADA cDNA is introduced are not immortal — they have a finite lifespan.
As these cells die over time, the production of the ADA enzyme decreases, and the immune system function is once again impaired.
For a permanent cure, the ADA gene would need to be introduced into early embryonic marrow cells that continuously replenish lymphocytes.

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Question 12

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How does PCR aid in the molecular diagnosis of diseases?

PCR amplifies nucleic acids from pathogens or mutated genes even when they are present in very low concentrations, before disease symptoms become visible.
This allows early detection of infections like HIV in suspected AIDS patients or mutations in genes of suspected cancer patients.
Because the method amplifies specific sequences exponentially, it can detect a pathogen at a stage when conventional methods like serum or urine analysis would fail.

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Question 13

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Explain the principle of ELISA in disease diagnosis.

ELISA is based on the principle of specific antigen-antibody interaction, where an antigen binds specifically to its corresponding antibody.
Infection by a pathogen can be detected either by identifying pathogen antigens (proteins, glycoproteins) or by detecting the antibodies synthesised by the body against the pathogen.
An enzyme-linked antibody produces a measurable colour change upon binding, allowing quantitative or qualitative detection of the pathogen.

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Chapter sections

Chapter 10: Biotechnology and its Applications | Short Questions

What is totipotency? How is it exploited in plant biotechnology?

Distinguish between somaclones and somatic hybrids.

Why is meristem used for obtaining virus-free plants in tissue culture?

Why does Bt toxin not kill the Bacillus thuringiensis bacterium that produces it?

Name the cry genes responsible for controlling cotton bollworm and corn borer. What do these genes encode?

What is RNAi? Why is it described as a method of cellular defense?

How was RNAi used to protect tobacco plants from the nematode Meloidogyne incognita?

State two advantages of recombinant therapeutics over products isolated from non-human sources.

Why was the production of human insulin using recombinant DNA technology challenging?

What was the significance of the first clinical gene therapy in 1990?

Why must a patient who receives gene therapy for ADA deficiency undergo periodic infusions of engineered lymphocytes?

How does PCR aid in the molecular diagnosis of diseases?

Explain the principle of ELISA in disease diagnosis.

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