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NCERT Solutions for Class 12 Biology Chapter 12
Biotechnology and its Applications Class 12
Chapter 12 Biotechnology and its Applications Exercise Solutions
Exercise : Solutions of Questions on Page Number : 215
Q1 :
Crystals of Bt toxin produced by some bacteria do not kill the bacteria themselves because -
(a) bacteria are resistant to the toxin
(b) toxin is immature:
(c) toxin is inactive:
(d) bacteria encloses toxin in a special sac.
Answer :
toxin is inactive:
In bacteria, the toxin is present in an inactive form, called prototoxin, which gets converted into active form when it
enters the body of an insect.
Q2 :
What are transgenic bacteria? Illustrate using any one example.
Answer :
Transgenic bacteria contain foreign gene that is intentionally introduced into its genome. They are manipulated to
express the desirable gene for the production of various commercially important products.
An example of transgenic bacteria is E.coli. In the plasmid of E.coli, the two DNA sequences corresponding to A and
B chain of human insulin are inserted, so as to produce the respective human insulin chains. Hence, after the
insertion of insulin gene into the bacterium, it becomes transgenic and starts producing chains of human insulin. Later
on, these chains are extracted from E.coli and combined to form human insulin.
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, www.ncrtsolutions.in
Q3 :
Compare and contrast the advantages and disadvantages of production of genetically modified crops.
Answer :
The production of genetically modified (GM) or transgenic plants has several advantages.
(i) Most of the GM crops have been developed for pest resistance, which increases the crop productivity and
therefore, reduces the reliance on chemical pesticides.
(ii) Many varieties of GM food crops have been developed, which have enhanced nutritional quality. For example,
golden rice is a transgenic variety in rice, which is rich in vitamin A.
(iii) These plants prevent the loss of fertility of soil by increasing the efficiency of mineral usage.
(iv) They are highly tolerant to unfavourable abiotic conditions.
(v) The use of GM crops decreases the post harvesting loss of crops.
However, there are certain controversies regarding the use of genetically modified crops around the world. The use of
these crops can affect the native biodiversity in an area. For example, the use of Bt toxin to decrease the amount of
pesticide is posing a threat for beneficial insect pollinators such as honey bee. If the gene expressed for Bt toxin gets
expressed in the pollen, then the honey bee might be affected. As a result, the process of pollination by honey bees
would be affected. Also, genetically modified crops are affecting human health. They supply allergens and certain
antibiotic resistance markers in the body. Also, they can cause genetic pollution in the wild relatives of the crop
plants. Hence, it is affecting our natural environment.
Q4 :
What are Cry proteins? Name an organism that produces it. How has man exploited this protein to his
benefit?
Answer :
Cry proteins are encoded by cry genes. These proteins are toxins, which are produced by Bacillus
thuringiensis bacteria. This bacterium contains these proteins in their inactive from. When the inactive toxin protein is
ingested by the insect, it gets activated by the alkaline pH of the gut. This results in the lysis of epithelial cell and
eventually the death of the insect. Therefore, man has exploited this protein to develop certain transgenic crops with
insect resistance such as Bt cotton, Bt corn, etc.
Q5 :
What is gene therapy? Illustrate using the example of adenosine deaminase (ADA) deficiency.
Answer :
Gene therapy is a technique for correcting a defective gene through gene manipulation. It involves the delivery of a
normal gene into the individual to replace the defective gene, for example, the introduction of gene for adenosine
deaminase (ADA) in ADA deficient individual. The adenosine deaminase enzyme is important for the normal
www.ncrtsolutions.in
NCERT Solutions for Class 12 Biology Chapter 12
Biotechnology and its Applications Class 12
Chapter 12 Biotechnology and its Applications Exercise Solutions
Exercise : Solutions of Questions on Page Number : 215
Q1 :
Crystals of Bt toxin produced by some bacteria do not kill the bacteria themselves because -
(a) bacteria are resistant to the toxin
(b) toxin is immature:
(c) toxin is inactive:
(d) bacteria encloses toxin in a special sac.
Answer :
toxin is inactive:
In bacteria, the toxin is present in an inactive form, called prototoxin, which gets converted into active form when it
enters the body of an insect.
Q2 :
What are transgenic bacteria? Illustrate using any one example.
Answer :
Transgenic bacteria contain foreign gene that is intentionally introduced into its genome. They are manipulated to
express the desirable gene for the production of various commercially important products.
An example of transgenic bacteria is E.coli. In the plasmid of E.coli, the two DNA sequences corresponding to A and
B chain of human insulin are inserted, so as to produce the respective human insulin chains. Hence, after the
insertion of insulin gene into the bacterium, it becomes transgenic and starts producing chains of human insulin. Later
on, these chains are extracted from E.coli and combined to form human insulin.
www.ncrtsolutions.in
, www.ncrtsolutions.in
Q3 :
Compare and contrast the advantages and disadvantages of production of genetically modified crops.
Answer :
The production of genetically modified (GM) or transgenic plants has several advantages.
(i) Most of the GM crops have been developed for pest resistance, which increases the crop productivity and
therefore, reduces the reliance on chemical pesticides.
(ii) Many varieties of GM food crops have been developed, which have enhanced nutritional quality. For example,
golden rice is a transgenic variety in rice, which is rich in vitamin A.
(iii) These plants prevent the loss of fertility of soil by increasing the efficiency of mineral usage.
(iv) They are highly tolerant to unfavourable abiotic conditions.
(v) The use of GM crops decreases the post harvesting loss of crops.
However, there are certain controversies regarding the use of genetically modified crops around the world. The use of
these crops can affect the native biodiversity in an area. For example, the use of Bt toxin to decrease the amount of
pesticide is posing a threat for beneficial insect pollinators such as honey bee. If the gene expressed for Bt toxin gets
expressed in the pollen, then the honey bee might be affected. As a result, the process of pollination by honey bees
would be affected. Also, genetically modified crops are affecting human health. They supply allergens and certain
antibiotic resistance markers in the body. Also, they can cause genetic pollution in the wild relatives of the crop
plants. Hence, it is affecting our natural environment.
Q4 :
What are Cry proteins? Name an organism that produces it. How has man exploited this protein to his
benefit?
Answer :
Cry proteins are encoded by cry genes. These proteins are toxins, which are produced by Bacillus
thuringiensis bacteria. This bacterium contains these proteins in their inactive from. When the inactive toxin protein is
ingested by the insect, it gets activated by the alkaline pH of the gut. This results in the lysis of epithelial cell and
eventually the death of the insect. Therefore, man has exploited this protein to develop certain transgenic crops with
insect resistance such as Bt cotton, Bt corn, etc.
Q5 :
What is gene therapy? Illustrate using the example of adenosine deaminase (ADA) deficiency.
Answer :
Gene therapy is a technique for correcting a defective gene through gene manipulation. It involves the delivery of a
normal gene into the individual to replace the defective gene, for example, the introduction of gene for adenosine
deaminase (ADA) in ADA deficient individual. The adenosine deaminase enzyme is important for the normal
www.ncrtsolutions.in
