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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.
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
functioning of the immune system.
The individual suffering from this disorder
can be cured by transplantation of bone marrow cells.
The first 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 specific template DNA. It involves the use of a vector
to carry the specific 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 specific gene responsible for the synthesis.
Q8 :
Find out from internet what is golden
rice.
Answer :
Golden rice is a genetically modified variety of
rice, Oryza
sativa,which has been developedas a
fortified 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 fulfill 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 significant 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 :
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.