Part 3 – Biotechnological Applications in Agriculture: Bt Crops

Q1.

Bt crops are genetically modified to produce:
a) Antibiotic proteins
b) Insecticidal proteins
c) Growth hormones
d) Nitrogen-fixing enzymes

Answer: b) Insecticidal proteins

Explanation:

(a) Antibiotics → Not Bt’s role.
(b) Correct → Bt crops produce Cry proteins toxic to insects.
(c) Growth hormones → Not related.
(d) Nitrogen fixation → Done by Rhizobium, not Bt.

Q2.

The insecticidal gene in Bt crops is derived from:
a) Escherichia coli
b) Bacillus thuringiensis
c) Agrobacterium tumefaciens
d) Rhizobium

Answer: b) Bacillus thuringiensis

Explanation:

(a) E. coli → Not related to insecticidal proteins.
(b) Correct → Bt stands for Bacillus thuringiensis.
(c) Agrobacterium → Used as vector, not toxin source.
(d) Rhizobium → Nitrogen fixer.

Q3.

The toxin produced by Bt is called:
a) Cry protein
b) Insulin
c) ADA enzyme
d) Toxin A

Answer: a) Cry protein

Explanation:

(a) Correct → Cry (crystal) proteins are toxic to insects.
(b) Insulin → Not related.
(c) ADA → Enzyme in gene therapy, not here.
(d) Toxin A → Not Bt toxin.

Q4.

Cry proteins are toxic to insects because they:
a) Inhibit photosynthesis
b) Disrupt insect gut lining
c) Kill insect nervous system directly
d) Block hormone synthesis

Answer: b) Disrupt insect gut lining

Explanation:

(a) Photosynthesis → Plant process, not insect.
(b) Correct → Cry proteins form pores in insect midgut epithelium.
(c) Nervous system → Not direct effect.
(d) Hormones → Not affected.

Q5.

Why are Cry proteins safe for humans?
a) Humans lack receptors for Cry toxins
b) They are digested in acidic human stomach
c) They act only in alkaline insect gut
d) All of the above

Answer: d) All of the above

Explanation:

(a) True → No receptors in human intestine.
(b) True → Digested in our stomach acid.
(c) True → Active only in alkaline insect gut.
(d) Correct → All reasons make them safe.

Q6.

Which Bt gene is effective against corn borer insects?
a) Cry1Ac
b) Cry2Ab
c) Cry1Ab
d) Cry2Aa

Answer: c) Cry1Ab

Explanation:

(a) Cry1Ac → Cotton bollworm.
(b) Cry2Ab → Cotton pests.
(c) Cry1Ab → Correct, targets corn borer.
(d) Cry2Aa → Different specificity.

Q7.

Bt cotton is resistant to which pest?
a) Rice stem borer
b) Cotton bollworm
c) Aphids
d) Nematodes

Answer: b) Cotton bollworm

Explanation:

(a) Rice stem borer → Controlled by Cry1Ab in rice.
(b) Correct → Bollworms killed by Cry1Ac and Cry2Ab.
(c) Aphids → Not controlled by Bt.
(d) Nematodes → Controlled by RNA interference, not Bt.

Q8.

In Bt plants, the cry gene is introduced using:
a) Retrovirus
b) Ti plasmid of Agrobacterium tumefaciens
c) Human insulin vector
d) Liposomes

Answer: b) Ti plasmid of Agrobacterium tumefaciens

Explanation:

(a) Retrovirus → Animal systems.
(b) Correct → Ti plasmid used for plant transformation.
(c) Insulin vector → Not relevant.
(d) Liposomes → Animal cells, not plants.

Q9.

Why do Cry proteins not kill Bt bacteria themselves?
a) They lack toxin genes
b) They produce inactive protoxins
c) They are resistant due to special enzymes
d) Their gut pH is alkaline

Answer: b) They produce inactive protoxins

Explanation:

(a) Incorrect → They have toxin genes.
(b) Correct → Protoxins are inactive until ingested by insects.
(c) Incorrect → Enzymes not involved.
(d) Incorrect → Bacteria don’t have insect-like gut.

Q10.

The activation of Cry protoxins in insects requires:
a) Alkaline gut pH
b) Specific proteases
c) Binding to gut receptors
d) All of the above

Answer: d) All of the above

Explanation:

(a) Alkaline gut → Required.
(b) Proteases → Convert protoxin to active toxin.
(c) Gut receptors → Necessary for binding.
(d) Correct → All steps required.

Q11.

Which year was Bt cotton first commercially released in India?
a) 1995
b) 2002
c) 2008
d) 2015

Answer: b) 2002

Explanation:

(a) Too early.
(b) Correct → Bt cotton approved in India in 2002.
(c) 2008 → Too late.
(d) 2015 → Not correct.

Q12.

A major benefit of Bt cotton cultivation in India is:
a) Increased pesticide use
b) Reduced yield
c) Reduced pesticide consumption
d) Resistance to fungal diseases

Answer: c) Reduced pesticide consumption

Explanation:

(a) Incorrect → Pesticide use decreases.
(b) Incorrect → Yield increases.
(c) Correct → Less need for insecticides.
(d) Incorrect → Bt does not protect against fungi.

Q13.

Which of the following crops has been successfully modified with Bt genes?
a) Potato
b) Rice
c) Maize
d) All of the above

Answer: d) All of the above

Explanation:

(a) Potato → Yes, Bt potato created.
(b) Rice → Bt rice developed.
(c) Maize → Bt maize widely grown.
(d) Correct → All modified.

Q14.

Which is the most significant concern regarding Bt crops?
a) Reduced yield
b) Development of insect resistance
c) High fertilizer requirement
d) Drought susceptibility

Answer: b) Development of insect resistance

Explanation:

(a) Incorrect → Yield generally increases.
(b) Correct → Insects may evolve resistance to Cry proteins.
(c) Incorrect → Fertilizer need unaffected.
(d) Incorrect → Not linked.

Q15.

To delay resistance development in insects, farmers are advised to:
a) Use higher doses of Bt toxin
b) Rotate Bt crops with non-Bt crops
c) Stop using fertilizers
d) Spray chemical pesticides daily

Answer: b) Rotate Bt crops with non-Bt crops

Explanation:

(a) Incorrect → Increases resistance.
(b) Correct → Refugia strategy delays resistance.
(c) Incorrect → Fertilizer unrelated.
(d) Incorrect → Daily pesticide unnecessary.

Q16.

Which Cry gene combination is used in Bollgard II cotton?
a) Cry1Ac + Cry2Ab
b) Cry1Ab + Cry2Aa
c) Cry1Ab + Cry1Ac
d) Cry2Ab + Cry2Aa

Answer: a) Cry1Ac + Cry2Ab

Explanation:

(a) Correct → Bollgard II cotton contains both genes.
(b) Incorrect → Not used together.
(c) Incorrect → Combination not in Bollgard II.
(d) Incorrect → Wrong pair.

Q17.

Bt crops mainly protect against:
a) Nematodes
b) Viral infections
c) Lepidopteran insect larvae
d) Bacterial infections

Answer: c) Lepidopteran insect larvae

Explanation:

(a) Incorrect → RNAi technology targets nematodes.
(b) Incorrect → No virus resistance.
(c) Correct → Bt targets Lepidoptera (moths, butterflies).
(d) Incorrect → Not bacterial protection.

Q18.

Which statement about Bt toxin is FALSE?
a) It is produced as inactive protoxin
b) It becomes active in insect alkaline gut
c) It is toxic to all animals including humans
d) It binds specific receptors in insect midgut

Answer: c) It is toxic to all animals including humans

Explanation:

(a) True → Produced as protoxin.
(b) True → Activated in insect gut.
(c) False → Safe for humans.
(d) True → Receptor binding essential.

Q19.

Bt brinjal was first approved for commercial cultivation in:
a) India
b) Bangladesh
c) USA
d) China

Answer: b) Bangladesh

Explanation:

(a) India → Approval withheld due to biosafety concerns.
(b) Correct → Bangladesh approved Bt brinjal in 2013.
(c) USA → No Bt brinjal cultivation.
(d) China → Not first.

Q20.

The advantage of stacking multiple Cry genes in crops is:
a) Faster growth of plants
b) Broader spectrum insect resistance
c) Resistance to herbicides
d) Better nutritional content

Answer: b) Broader spectrum insect resistance

Explanation:

(a) Incorrect → Growth not related.
(b) Correct → More Cry genes = kills more insect species.
(c) Incorrect → Herbicide resistance is different trait.
(d) Incorrect → Nutrition unaffected.

Q21.

Which of the following is a limitation of Bt crops?
a) Cannot be grown in tropical regions
b) May affect non-target insects
c) Low productivity
d) Need for excess fertilizers

Answer: b) May affect non-target insects

Explanation:

(a) Incorrect → Grown in tropics like India.
(b) Correct → Non-target effects are concern.
(c) Incorrect → Productivity is higher.
(d) Incorrect → Fertilizer need same as normal crops.

Q22.

Bt corn was mainly developed to resist:
a) Stem borers
b) Weeds
c) Aphids
d) Viruses

Answer: a) Stem borers

Explanation:

(a) Correct → Bt corn resists European corn borer.
(b) Incorrect → Herbicide resistance is separate.
(c) Incorrect → Bt does not target aphids.
(d) Incorrect → Not antiviral.

Q23.

Bt toxin genes belong to which gene family?
a) Cry genes
b) Lux genes
c) Lac genes
d) bla genes

Answer: a) Cry genes

Explanation:

(a) Correct → Cry genes code Bt toxins.
(b) Lux → Bioluminescence.
(c) Lac → Lactose metabolism.
(d) bla → Beta-lactamase (antibiotic resistance).

Q24.

A farmer growing Bt cotton will benefit the most by:
a) Higher seed cost and lower yield
b) Reduced pesticide cost and higher yield
c) Reduced water use
d) Increased herbicide tolerance

Answer: b) Reduced pesticide cost and higher yield

Explanation:

(a) Incorrect → Yield is higher, not lower.
(b) Correct → Less pesticide needed + better yield.
(c) Incorrect → Water use not reduced.
(d) Incorrect → Herbicide tolerance not from Bt.

Q25.

Which of the following is NOT a direct advantage of Bt crops?
a) Reduced pesticide use
b) Higher crop yield
c) Increased biodiversity automatically
d) Protection from insect pests

Answer: c) Increased biodiversity automatically

Explanation:

(a) True → Less pesticide use.
(b) True → Higher yield.
(c) False → Biodiversity protection is indirect, not automatic.
(d) True → Pest resistance is main advantage.

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Part 3 – Biotechnological Applications in Agriculture: Bt Crops