Bt crops and pest-resistant plants — practice questions

Question 1 · difficulty L1 · recall

What is the source organism of the Bt toxin genes used in pest-resistant crops?

• A. Bacillus thuringiensis
• B. Agrobacterium tumefaciens
• C. Rhizobium leguminosarum
• D. Escherichia coli

Question 2 · difficulty L1 · recall

Why does the Bt protoxin become active inside the gut of a susceptible insect larva?

• A. The acidic gut converts it into glucose
• B. Alkaline gut conditions activate it
• C. Plant enzymes activate it before ingestion
• D. The toxin is activated only by sunlight

Question 3 · difficulty L2 · understanding

What happens after activated Bt toxin binds to receptors on the insect midgut epithelium?

• A. The toxin is converted into starch
• B. The insect begins nitrogen fixation
• C. Pores form in the epithelial cells
• D. The gut becomes completely impermeable to ions

Question 4 · difficulty L3 · application

A cotton plant carries a cry gene but a particular insect species is unaffected. What is the best explanation?

• A. Bt proteins affect only fungal pathogens
• B. All cry genes kill every insect species
• C. The plant cannot express bacterial genes
• D. That Cry protein may not target the insect

Question 5 · difficulty L3 · application

Why can Bt crops reduce the need for some chemical insecticide applications?

• A. The plant makes a pest-specific toxin
• B. The plant becomes immune to every pathogen
• C. The crop stops attracting all insects
• D. The soil becomes sterile around the roots

Question 6 · difficulty L3 · application

A Bt crop controls bollworm larvae but not sap-sucking insects. Which principle does this illustrate?

• A. Bt crops cannot express foreign genes
• B. Bt toxin action is target-specific
• C. All insects require identical receptors
• D. Chemical pesticides are always more specific

Question 7 · difficulty L3 · understanding

The toxin proteins isolated from Bacillus thuringiensis, coded by which of the following genes would contrl cotton bollworms and corn borer, respectively?

• A. cryIAc and cryIAb
• B. crylAc and cryllAb
• C. cryllAb and crylAc
• D. cryIAc and cryIIIAb

Question 8 · difficulty L3 · understanding

Following are the steps involved in action of toxin in Bt. Cotton A. The inactive toxin converted into active form due to alkaline pH of gut of insect. B. Bacillus thuringiensis produce crystals with toxic insecticidal proteins. C. The alkaline pH solubilises the crystals. D. The activated toxin binds to the surface of midgut cells, creates pores and causes death of the insect. E. The toxin proteins exist as inactive protoxins in bacteria. Choose the correct sequence of steps from the options given below:

• A. $$\mathrm{E} \rightarrow \mathrm{C} \rightarrow \mathrm{B} \rightarrow \mathrm{A} \rightarrow \mathrm{D}$$
• B. $$\mathrm{B} \rightarrow \mathrm{C} \rightarrow \mathrm{A} \rightarrow \mathrm{E} \rightarrow \mathrm{D}$$
• C. $$\mathrm{A} \rightarrow \mathrm{E} \rightarrow \mathrm{B} \rightarrow \mathrm{D} \rightarrow \mathrm{C}$$
• D. $$\mathrm{B} \rightarrow \mathrm{E} \rightarrow \mathrm{C} \rightarrow \mathrm{A} \rightarrow \mathrm{D}$$

Question 9 · difficulty L3 · understanding

Given below are two statements: Statement I : Bt toxins are insect group specific and coded by a gene cry IAc. Statement II : Bt toxin exists as inactive protoxin in B. thuringiensis. However, after ingestion by the insect the inactive protoxin gets converted into active form due to acidic $$\mathrm{pH}$$ 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 true
• B. Both Statement I and Statement II are false
• C. Statement I is true but Statement II is false
• D. Statement I is false but Statement II is true

Question 10 · difficulty L3 · understanding

Match List I with List II List - I List - II A. $$\alpha$$ -I 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 form the options given below:

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