Biotechnology and its Applications

Class 12

18 previous-year questions from this chapter every option and the correct answer, free · where the marks are

1. Applications in agriculture: Bt crops, RNAi

Exam focus: Bt cotton's toxin is made as an inactive protoxin and only becomes active once it meets the alkaline pH of an insect's gut — which is also why it is considered harmless if eaten by humans, whose acidic gut never activates it. RNAi-based nematode resistance uses the same silencing logic in reverse: a nematode-specific gene introduced into tobacco as both sense and antisense RNA forms double-stranded RNA that triggers interference, silencing the nematode's own mRNA when it feeds on the transgenic plant.

Biotechnology Applications in Agriculture: Bt Crops and RNAi

PW English Medium

Covers the introduction plus applications in agriculture (Bt crops, RNAi) specifically, as the first lecture in a chaptered series.

ZoologyNEET 2025show ▾

Silencing of specific mRNA is possible via RNAi because of:

A.Complementary dsRNA✓
B.Inhibitory ssRNA
C.Complementary tRNA
D.Non-complementary ssRNA

Solution

RNAi silences a gene through a double-stranded RNA complementary to the target mRNA; the dsRNA is processed into fragments that bind the mRNA and block translation.

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BotanyNEET 2024show ▾

Given below are two statements: Statement I: Bt toxins are insect-group specific and coded by a gene cryIAc. Statement II: Bt toxin exists as an inactive protoxin in B. thuringiensis. However, after ingestion by the insect the inactive protoxin gets converted into the active form due to the acidic pH of the insect gut. In the light of the above statements, choose the correct answer from the options given below:

A.Both Statement I and Statement II are false
B.Statement I is true but Statement II is false✓
C.Statement I is false but Statement II is true
D.Both Statement I and Statement II are true

Solution

Bt toxins are indeed insect-group specific and encoded by cry genes (Statement I true). The inactive protoxin is activated by the alkaline pH of the insect gut, not acidic — Statement II is false.

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BotanyNEET 2022show ▾

Transposons can be used during which one of the following?

A.Gene sequencing
B.Polymerase chain reaction
C.Gene silencing✓
D.Autoradiography

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ZoologyNEET 2020show ▾

The Bt cotton variety, developed by introducing the toxin gene of Bacillus thuringiensis (Bt), is resistant to:

A.Insect pests✓
B.Fungal diseases
C.Plant nematodes
D.Insect predators

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ZoologyNEET 2019show ▾

Which of the following is true for Golden Rice?

A.It is vitamin A-enriched, with a gene from daffodil✓
B.It is pest-resistant, with a gene from Bacillus thuringiensis
C.It is drought-tolerant, developed using an Agrobacterium vector
D.It has yellow grains because of a gene introduced from a primitive variety of rice

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ZoologyNEET 2019show ▾

What triggers activation of the protoxin to the active Bt toxin of Bacillus thuringiensis in the bollworm gut?

A.Body temperature
B.Moist surface of the midgut
C.Alkaline pH of the gut✓
D.Acidic pH of the stomach

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2. Applications in medicine: insulin, gene therapy, molecular diagnosis

Exam focus: Eli Lilly's recombinant insulin (Humulin) is made by synthesising the A and B chains separately in two E. coli strains and joining them with disulfide bonds afterward, skipping the C-peptide-containing proinsulin stage the human pancreas normally goes through and excises. Gene therapy's textbook case, ADA deficiency, is not a permanent cure: the corrected lymphocytes are not immortal, so the patient needs periodic fresh infusions unless the correction is made at the embryo stage instead.

Genetically Engineered Insulin (Biotechnology Applications)

Magnet Brains

How E. coli is engineered to produce human insulin (Humulin) — the most-tested example here. Gene therapy and molecular diagnosis are separate lectures in the same series.

ZoologyNEET 2025show ▾

Why can't insulin be given orally to diabetic patients?

A.The human body will elicit a strong immune response
B.It will be digested in the gastro-intestinal (GI) tract✓
C.Because of structural variation
D.Its bioavailability will be increased

Solution

Insulin is a peptide hormone; taken by mouth it would be digested by gastric and pancreatic proteases before it could act, so it must be injected.

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BotanyNEET 2025show ▾

Which of the following genetically engineered organisms was used by Eli Lilly to prepare human insulin?

A.Bacterium✓
B.Yeast
C.Virus
D.Phage

Solution

Eli Lilly produced human insulin (Humulin) in 1983 by expressing the A and B chains in E. coli, a bacterium, and then joining them by disulphide bonds.

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ZoologyNEET 2024show ▾

Match List I with List II.

List I	List II
$A . α - 1$ antitrypsin	I. Cotton bollworm
B. Cry IAb	II. ADA deficiency
C. Cry IAc	III. Emphysema
D. Enzyme replacement therapy	IV. Corn borer

Choose the correct answer from the options given below:

A.A-III, B-I, C-II, D-IV
B.A-III, B-IV, C-I, D-II✓
C.A-II, B-IV, C-I, D-III
D.A-II, B-I, C-IV, D-III

Solution

$α - 1$ antitrypsin is used to treat emphysema (III); cry IAb controls corn borer (IV); cry IAc controls cotton bollworm (I); enzyme replacement therapy treats ADA deficiency (II).

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ZoologyNEET 2023show ▾

Which one of the following techniques does not serve the purpose of early diagnosis of a disease for its early treatment?

A.Recombinant DNA technology
B.Serum and urine analysis✓
C.Polymerase chain reaction (PCR) technique
D.Enzyme-linked immunosorbent assay (ELISA) technique

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ZoologyNEET 2022show ▾

In gene therapy of adenosine deaminase (ADA) deficiency, the patient requires periodic infusion of genetically engineered lymphocytes because:

A.Genetically engineered lymphocytes are not immortal cells✓
B.A retroviral vector is introduced into these lymphocytes
C.The gene isolated from marrow cells producing ADA is introduced into cells at embryonic stages
D.Lymphocytes from the patient's blood are grown in culture, outside the body

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ZoologyNEET 2022show ▾

Statements related to human insulin are given below. Which statement(s) is/are correct about genetically engineered insulin? (a) Pro-hormone insulin contains an extra stretch of C-peptide (b) A-peptide and B-peptide chains of insulin were produced separately in E. coli, extracted and combined by creating disulphide bonds between them (c) Insulin used for treating diabetes was extracted from cattle and pigs (d) Pro-hormone insulin needs to be processed for conversion into a mature and functional hormone (e) Some patients develop allergic reactions to the foreign insulin Choose the most appropriate answer from the options given below:

A.(c), (d) and (e) only
B.(a), (b) and (d) only
C.(b) only✓
D.(c) and (d) only

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BotanyNEET 2021show ▾

Nowadays it is possible to detect the mutated gene causing cancer by allowing a radioactive probe to hybridise with its complementary DNA in a clone of cells, followed by its detection using autoradiography, because:

A.The mutated gene partially appears on a photographic film
B.The mutated gene completely and clearly appears on a photographic film
C.The mutated gene does not appear on a photographic film as the probe has no complementarity with it✓
D.The mutated gene does not appear on a photographic film as the probe has complementarity with it

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BotanyNEET 2021show ▾

When gene targeting involving gene amplification is attempted in an individual's tissue to treat disease, it is known as:

A.Biopiracy
B.Gene therapy✓
C.Molecular diagnosis
D.Safety testing

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ZoologyNEET 2021show ▾

For effective treatment of a disease, early diagnosis and understanding its pathophysiology is very important. Which of the following molecular diagnostic techniques is very useful for early detection?

A.Western blotting technique
B.Southern blotting technique
C.ELISA technique✓
D.Hybridisation technique

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ZoologyNEET 2021show ▾

With regard to insulin, choose the correct options. (a) C-peptide is not present in mature insulin (b) The insulin produced by rDNA technology has C-peptide (c) The pro-insulin has C-peptide (d) A-peptide and B-peptide of insulin are interconnected by disulphide bridges Choose the correct answer from the options given below:

A.(b) and (d) only
B.(b) and (c) only
C.(a), (c) and (d) only✓
D.(a) and (d) only

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ZoologyNEET 2020show ▾

Match the following columns and select the correct option.

Item	Association
(a) Bt cotton	(i) Gene therapy
(b) Adenosine deaminase deficiency	(ii) Cellular defence
(c) RNAi	(iii) Detection of HIV infection
(d) PCR	(iv) Bacillus thuringiensis

A.(a)-(iv), (b)-(i), (c)-(ii), (d)-(iii)✓
B.(a)-(iii), (b)-(ii), (c)-(i), (d)-(iv)
C.(a)-(ii), (b)-(iii), (c)-(iv), (d)-(i)
D.(a)-(i), (b)-(ii), (c)-(iii), (d)-(iv)

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ZoologyNEET 2020show ▾

Which of the following statements is not correct?

A.In man, insulin is synthesised as a proinsulin
B.The proinsulin has an extra peptide called the C-peptide
C.The functional insulin has the A and B chains linked together by hydrogen bonds✓
D.Genetically engineered insulin is produced in E. coli

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3. Transgenic animals and ethical issues

Exam focus: NCERT's transgenic-animal examples are specific and get tested as specific facts: "Rosie," a transgenic cow, was engineered to produce human alpha-lactalbumin-enriched milk, and transgenic mice now carry out the safety testing for the polio vaccine that once required monkeys — knowing the named example, which animal and which product, is what separates a right answer from a vaguely-right-sounding one.

Transgenic Animals, Biosafety and Ethical Issues

NCERT Wallah

Directly matches the subtopic — a dedicated lecture on transgenic animals and ethical issues (biosafety, biopiracy, patents).