NCERT Solutions for Class 12 Biology Chapter 10 Biotechnology and its Applications

NCERT
SOLUTIONS
CLASS - 12th

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Class : 12th
Subject : Biology
Chapter : 12
Chapter Name : Biotechnology and its Applications

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.

Page : 215 , Block Name : Exercise

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.

Page : 215 , Block Name : Exercise

Q3 Compare and contrast the advantages and disadvantages of production of genetically modi ed
crops.

Answer. The production of genetically modi ed (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 ef ciency 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 modi ed 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 bene cial 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 modi ed
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.

Page : 215 , Block Name : Exercise

Q4 What are Cry proteins? Name an organism that produces it. How has man exploited this
protein to his bene t?

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) de ciency.

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 de cient individual.
The adenosine deaminase enzyme is important for the normal functioning of the immune system.
The individual suffering from this disorder can be cured by transplantation of bone marrow cells.
The rst step involves the extraction of lymphocyte from the patient's bone marrow. Then, a
functional gene for ADA is introduced into lymphocytes with the help of retrovirus. These treated
lymphocytes containing ADA gene are then introduced into the patient's bone marrow. Thus, the
gene gets activated producing functional T- lymphocytes and activating the patient's immune
system.

Q6 Diagrammatically represent the experimental steps in cloning and expressing an human gene
(say the gene for growth hormone) into a bacterium like E. coli ?

Answer. DNA cloning is a method of producing multiple identical copies of speci c template DNA.
It involves the use of a vector to carry the speci c foreign DNA fragment into the host cell. The
mechanism of cloning and transfer of gene for growth hormone into E.coli is represented below.

Q7 Can you suggest a method to remove oil (hydrocarbon) from seeds based on your
understanding of rDNA technology and chemistry of oil?

Answer. Recombinant DNA technology (rDNA) is a technique used for manipulating the genetic
material of an organism to obtain the desired result. For example, this technology is used for
removing oil from seeds. The constituents of oil are glycerol and fatty acids. Using rDNA, one can
obtain oilless seeds by preventing the synthesis of either glycerol or fatty acids. This is done by

removing the speci c gene responsible for the synthesis.

Q8 Find out from internet what is golden rice.

Answer. Golden rice is a genetically modi ed variety of rice, Oryza sativa,which has been
developed as a forti ed food for areas where there is a shortage of dietary vitamin A It contains a
precursor of pro-vitamin A, called beta-carotene, which has been introduced into the rice through
genetic engineering. The rice plant naturally produces beta- carotene pigment in its leaves.
However, it is absent in the endosperm of the seed. This is because beta-carotene pigment helps in
the process of photosynthesis while photosynthesis does not occur in endosperm. Since beta-
carotene is a precursor of pro- vitamin A, it is introduced into the rice variety to ful ll the
shortage of dietary vitamin A. It is simple and a less expensive alternative to vitamin
supplements.However,
this variety of rice has faced a signi cant opposition from environment activists Therefore, they
are still not available in market for human consumption.

Q9 Does our blood have proteases and nucleases?

Answer. No, human blood does not include the enzymes, nucleases and proteases. In human
beings, blood serum contains different types of protease inhibitors, which protect the blood
proteins from being broken down by the action of proteases. The enzyme, nucleases, catalyses the
hydrolysis of nucleic acids that is absent in blood.

Q10 Consult internet and nd out how to make orally active protein pharmaceutical. What is the
major problem to be encountered?

Answer. Orally active protein pharmaceuticals contain biologically active materials such as
peptides or proteins, antibodies, and polymeric beads. It is administrated orally into the body
through various formulations. It involves the encapsulation of protein or peptide in liposomes or
formulations using penetration enhancers. These proteins or peptides are used for treatment of
various diseases and are also used as vaccines. However, the oral administration of these peptides
or proteins has some problems related to it. Once these proteins are ingested, the proteases
present in the stomach juices denature the protein. As a result, their effect will be nulli ed. Hence,
it is necessary to protect the therapeutic protein from digestive enzymes, if taken orally. This is
the reason for the proteins to be injected directly into the target site.