Biotechnology and its Applications — NEET Botany MCQs with answers

Biotechnology and its Applications is a Class 12 Botany chapter in the NEET (UG) syllabus. NEET720 has 462 reviewed practice questions on it, each with a quick answer and a step-by-step explanation. The 8 questions below are free and fixed, so you can bookmark this page; the full chapter, plus mistake tracking and spaced revision, is in the app.

Topics covered

Applications in Agriculture · Applications in Medicine · Ethical Issues · Ethical and Biosafety Issues · Biosafety, biopiracy and IPR issues · GM crops in agriculture · Medical applications · Biotechnological Applications in Agriculture · Ethical and Regulatory Issues in Biotechnology · Applications of Biotechnology - Agriculture · Applications of Biotechnology - Medicine · Applications of Biotechnology - Biosafety and IPR · Applications of Biotechnology - Biosafety · Applications of Biotechnology - Molecular diagnosis · Human Welfare/Biotechnology · Bt cotton genes · RNAi technology · GEAC regulation · Transgenic animals/plants · GM crops · Molecular farming · Applications overview · Transgenic crops in India · Biotechnology · Bt crops · GM crop field trials · RNAi in plants · Recombinant insulin production · ELISA diagnostics · PCR diagnostics · Golden Rice biosynthesis · Biosafety regulation · Bt toxin mechanism · Gene therapy · Molecular diagnosis · Biopiracy and IP · Transgenic animals · Bt cotton adoption impact · GM crop yield trend · Bt toxin dose-response

8 free Biotechnology and its Applications practice questions with answers

Choose an answer in your head before opening it. Each explanation says why the correct option is right and, where relevant, why the tempting wrong option is wrong.

1. Question 1 · easy · Applications in Agriculture

   The genus of bacteria from which the insecticidal 'cry' genes used to develop Bt cotton were obtained is:

   • A.Bacillus thuringiensis
   • B.Agrobacterium tumefaciens
   • C.Escherichia coli
   • D.Pseudomonas fluorescens
   Show answer and explanation

   Answer: A. Bacillus thuringiensis

   Bt cotton is named for Bacillus thuringiensis, the soil bacterium that naturally produces crystal (cry) proteins toxic to specific insect larvae.

   Bacillus thuringiensis is a Gram-positive soil bacterium that produces crystal proteins encoded by cry genes during a particular phase of its growth. These proteins are insecticidal. Genetic engineers isolated specific cry genes and introduced them into cotton to confer resistance against bollworms, producing Bt cotton. Agrobacterium tumefaciens (B) is commonly used as a vector to deliver the gene into the plant but is not the source of the toxin gene. E. coli (C) is a standard cloning/expression host unrelated to the natural toxin source. Pseudomonas fluorescens (D) has been engineered in some experimental contexts to carry Bt toxin genes but is not the original source.

   Common mistake: Mixing up the source bacterium (B. thuringiensis) with the transfer vector (Agrobacterium).

   Key point: Bt = Bacillus thuringiensis; cry genes code for the crystal insecticidal proteins.

2. Question 2 · medium · Applications in Agriculture

   Within the Bacillus thuringiensis cell itself, the cry protein toxin exists as an inactive protoxin. This is biologically significant chiefly because it:

   • A.increases the molecular weight of the toxin for easier crystallisation
   • B.prevents the toxin from harming the bacterium that produces it
   • C.allows the toxin to be stored indefinitely without losing potency
   • D.enables the toxin to cross the insect cuticle more easily
   Show answer and explanation

   Answer: B. prevents the toxin from harming the bacterium that produces it

   The cry toxin is produced and stored as an inactive protoxin, so it does not damage or kill the Bt bacterium itself; it is activated only later inside a susceptible insect's gut.

   Bacillus thuringiensis produces the cry toxin in an inactive protoxin form. If the toxin were active inside the bacterium, it would kill or damage the very cell producing it. The inactive form is a self-protective mechanism. Activation occurs only after ingestion by a susceptible insect, where the alkaline pH of the insect gut solubilises the protoxin into its active form. Option B misplaces the reason as storage stability, C wrongly invokes cuticle penetration (the toxin acts on midgut epithelium after ingestion, not through the cuticle), and D fabricates an irrelevant structural reasoning about crystallisation.

   Common mistake: Assuming the inactive form exists for stability/storage reasons rather than self-protection.

   Key point: The cry toxin is inactive inside Bt itself — this protects the bacterium from its own toxin.

3. Question 3 · medium · Applications in Agriculture

   After activation in the insect gut, the active Bt toxin ultimately kills the susceptible larva by:

   • A.triggering an immune/allergic overreaction throughout the insect body
   • B.inhibiting DNA replication in gut epithelial cells
   • C.blocking cellular respiration in muscle tissue
   • D.binding to midgut epithelial cell receptors and causing the cells to swell and lyse
   Show answer and explanation

   Answer: D. binding to midgut epithelial cell receptors and causing the cells to swell and lyse

   The activated toxin binds specific receptors on midgut epithelial cells, causing them to swell and burst (lyse), which kills the insect.

   Once solubilised by the alkaline gut pH, the active toxin binds to specific receptor sites on the midgut epithelium of the susceptible insect. This binding creates pores/causes swelling of the epithelial cells, leading to cell lysis. Disruption of the midgut lining causes the insect to stop feeding and eventually die. Options A, B, and D describe mechanisms (DNA replication inhibition, respiratory blockage in muscle, systemic immune reaction) that are not how the Bt toxin actually functions; the real action is localized receptor-mediated membrane disruption in the gut epithelium.

   Common mistake: Assuming the Bt toxin works like a generalized poison affecting distant organs rather than acting locally on gut epithelium.

   Key point: Bt toxin binds midgut epithelial receptors → cell swelling and lysis → insect death.

4. Question 4 · medium · Applications in Agriculture

   A cotton breeder wants to protect a new cotton variety specifically against cotton bollworm attack using Bt technology. Which pair of cry genes is most appropriate to introduce for this purpose?

   • A.cryIAc and cryIIAb
   • B.cryIAb alone
   • C.cryIAc and cryIAb together, for broad-spectrum corn and cotton protection
   • D.Any cry gene works equally well against any insect order
   Show answer and explanation

   Answer: A. cryIAc and cryIIAb

   cryIAc and cryIIAb are the specific cry genes controlling cotton bollworms, illustrating that different cry genes are specific to different target pests.

   Cry genes show pest specificity. cryIAc and cryIIAb control cotton bollworms, whereas cryIAb controls corn borer. This gene-to-pest specificity means that the correct gene combination must be chosen based on the target pest for a given crop. Option B picks the wrong gene (targeted at corn borer, not cotton bollworm). Option C incorrectly mixes a corn-borer-specific gene into a cotton-protection strategy. Option D denies the well-established specificity of cry genes, a key NEET concept.

   Common mistake: Treating all cry genes as interchangeable insecticidal genes regardless of the target pest.

   Key point: cryIAc & cryIIAb → cotton bollworm; cryIAb → corn borer — cry genes are pest-specific, not universal.

5. Question 5 · easy · Applications in Agriculture

   Bt cotton is a genetically modified cotton plant made resistant to attack primarily by:

   • A.fungal wilt pathogens
   • B.bollworms
   • C.root-knot nematodes
   • D.aphid-transmitted viral infections
   Show answer and explanation

   Answer: B. bollworms

   Bt cotton carries a cry gene from Bacillus thuringiensis that confers resistance to bollworm attack, a major cotton pest.

   Bt cotton was developed by introducing a specific cry gene from Bacillus thuringiensis into the cotton genome, making the plant resistant to bollworm insects that were historically responsible for major crop losses and heavy insecticide use in cotton cultivation. It does not confer resistance to fungal pathogens, nematodes, or viruses — those require entirely different strategies (RNAi against Meloidogyne incognita in the case of nematodes, which is a distinct application in tobacco, not cotton).

   Common mistake: Confusing Bt cotton's insect resistance with nematode resistance (which is achieved via RNAi in tobacco, a separate example).

   Key point: Bt cotton = insect (bollworm) resistant cotton, not disease- or nematode-resistant.

6. Question 6 · medium · Applications in Agriculture

   A student claims: 'Since Bacillus thuringiensis itself constantly produces the cry toxin, the bacterium must possess a special detoxification enzyme that continuously neutralises the toxin inside its own cytoplasm to survive.' This claim is incorrect chiefly because:

   • A.the toxin only becomes proteinaceous after leaving the bacterial cell, before which it is a harmless lipid
   • B.the bacterium does not actually produce the toxin at all; it only acquires it from soil insects
   • C.the toxin is stored as an inactive protoxin within the bacterium, so no detoxification step is needed for self-protection
   • D.detoxification does occur, but only during the bacterium's spore stage
   Show answer and explanation

   Answer: C. the toxin is stored as an inactive protoxin within the bacterium, so no detoxification step is needed for self-protection

   No detoxification enzyme is needed because the toxin is inherently produced and stored in an inactive protoxin form within the bacterium.

   The student's premise assumes an active toxin requiring neutralisation. In reality, B. thuringiensis avoids self-harm not through detoxification but because the cry protein is synthesised and stored as an inactive protoxin — it simply is not toxic in that form. Activation only occurs after ingestion by a susceptible insect, under the alkaline gut conditions there. Option A wrongly denies Bt as the producer organism. Option C invents an unsupported detoxification stage. Option D fabricates a lipid-protein conversion with no biological basis.

   Common mistake: Inventing an active-toxin-plus-detoxification-enzyme model instead of recognising the simpler inactive-protoxin explanation.

   Key point: Self-protection of Bt bacterium is due to the protoxin being inactive, not due to any detoxifying enzyme.

7. Question 7 · medium · Applications in Agriculture

   Statement I: The Bt crystal protein is toxic to the bacterium Bacillus thuringiensis itself while it remains inside the bacterial cell. Statement II: The Bt crystal protein becomes an active toxin only after solubilisation by the alkaline pH of a susceptible insect's gut. In light of the above statements, choose the correct option:

   • A.Both Statement I and Statement II are false
   • B.Statement I is true but Statement II is false
   • C.Both Statement I and Statement II are true
   • D.Statement I is false but Statement II is true
   Show answer and explanation

   Answer: D. Statement I is false but Statement II is true

   Statement I is false — the toxin is inactive (non-toxic) within Bt itself. Statement II is true — activation requires the alkaline insect gut environment.

   Statement I is false: the cry protein exists as an inactive protoxin inside the Bt bacterium, so it does not harm the producing cell. Statement II is true: the protoxin is converted to its active, insecticidal form specifically by the alkaline pH environment found in the gut of a susceptible insect after ingestion. Since only Statement II holds true, option C is correct.

   Common mistake: Assuming the toxin must already be active inside the bacterium since Bt 'produces' the toxin.

   Key point: Protoxin is harmless inside Bt; alkaline insect gut pH is what activates it.

8. Question 8 · medium · Applications in Agriculture

   Arrange the following events in the correct sequence, starting from a susceptible bollworm larva feeding on Bt cotton leaves to its eventual death: (i) Alkaline gut pH solubilises the protoxin into its active form. (ii) Larva ingests Bt toxin protein present in the cotton plant tissue. (iii) Midgut epithelial cells swell and undergo lysis. (iv) Active toxin binds to specific receptors on midgut epithelial cells.

   • A.(iv) → (ii) → (i) → (iii)
   • B.(ii) → (i) → (iv) → (iii)
   • C.(i) → (ii) → (iii) → (iv)
   • D.(ii) → (iv) → (i) → (iii)
   Show answer and explanation

   Answer: B. (ii) → (i) → (iv) → (iii)

   Correct order: ingestion → alkaline-pH activation → receptor binding → cell lysis and death.

   The larva must first ingest the inactive protoxin present in Bt cotton tissue (ii). Inside the gut, the alkaline pH solubilises/activates the protoxin (i). The now-active toxin binds specific receptors on midgut epithelial cells (iv). This binding causes the cells to swell and lyse, damaging the gut lining and eventually killing the insect (iii). Any sequence placing activation or receptor binding before ingestion, or receptor binding before activation, is biologically impossible.

   Common mistake: Jumbling activation and receptor-binding order, or placing either step before ingestion.

   Key point: Sequence: ingest inactive toxin → alkaline activation → receptor binding → cell lysis → death.

Questions about Biotechnology and its Applications for NEET

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Questions are original NEET720 compositions reviewed for correctness, syllabus fit and option quality. Counts update as the bank grows (462 active practice questions in this chapter today).