This set of Class 12 Biology Chapter 12 Multiple Choice Questions & Answers (MCQs) focuses on “Biotechnology Applications – Bt Cotton”.
1. Some strains of Bacillus thuringiensis can kill certain insects such as _______
c) fruit fly
Explanation: Lepidopterans are an order of insects consisting of moths and butterflies. Some insects of this order can be killed by the bacteria Bacillus thuringiensis. A few examples of lepidopterans are tobacco budworm, armyworm, bettles, etc.
2. Bt cotton is a _______
a) cloned plant
b) transgenic plant
c) hybrid plant
d) mutated plant
Explanation: Bt cotton is an example of a transgenic plant. These are plants whose DNA is modified using genetic engineering techniques (rDNA technology). This plasmid is used as a vector to insert a foreign gene within a plant.
3. Insect resistance transgenic cotton has been developed by inserting a piece of DNA from ______
a) an insect
b) wild relative of cotton
c) a virus
d) a soil bacterium
Explanation: Insect resistance transgenic cotton has been developed by inserting a piece of DNA from a soil bacterium. The bacterium used in this is Agrobacterium tumefaciens. This organism is responsible for causing crown gall disease in an insect.
4. The gene which was used to produce insect-resistant cotton plant was taken from ______
a) Anabaena azollae
b) Agrobacterium tumefaciens
c) Bacillus thuringiensis
d) Bacillus subtilis
Explanation: The gene from Bacillus thuringiensis was used to produce insect-resistant plants. This gene was later on inserted into a bacterium called Agrobacterium tumefaciens which act as a vector for the Bt gene.
5. The protein crystals of B. thuringiensis contain toxic _______ protein.
Explanation: The protein crystals of B. thuringiensis contain toxic insecticidal protein. This protein acts against insects such as lepidopterans. They cause crown gall disease to plants.
6. The Bt toxin does not kill the Bacillus because the Bt toxin protein exist as inactive ________
Explanation: The Bacillus is not killed by its own Bt toxin because this Bt toxin protein exists as inactive protoxins in it. This toxin converts into an active form in an alkaline pH. This later on form crystals which lead to the death of that insect.
7. To which cells does the activated Bt toxin bind?
a) Neuroglial cells
c) Skeletal muscle cells
d) Epithelial cells
Explanation: The activated Bt toxin binds to the midgut epithelial cells. These cells line the inner and outer surface of our bodies such as skin, alimentary canal, urinary tract, and organs.
8. A gall producing gene in Agrobacterium tumefaciens is _______
a) cry gene
b) nif gene
c) T DNA
d) beta gene
Explanation: T DNA is the transfer-DNA. The gall producing gene in Agrobacterium tumefaciens is present in T DNA. It is the DNA of Ti (tumor-inducing) plasmid. It is also found in A. rhizogenes.
9. Ti plasmid is found in ________
Explanation: Ti plasmid i.e. tumor-inducing plasmid is found in Agrobacterium tumefaciens. This plasmid acts as a vector for the Bt gene. This Ti plasmid consists of T DNA. This T DNA, when expressed in plants, leads to tumor formation.
10. Toxic content of B. thuringiensis is _______ in nature.
c) amino acid
Explanation: The toxic content of B. thuringiensis consists of protoxins. These protoxins are protein in nature. These are cry proteins that kill the insect by forming crystals in its gut. Protoxins are endotoxins which can be used as biopesticides.
11. Bt gene which produces a protein toxic to insect larvae is ______
Explanation: The Bt gene produces a protein toxic to insect larvae codes for cry protein. Cry protein is a toxic protein encoded by cry gene. This protein is toxic to various insects and is produced by B. thuringiensis bacteria.
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