NCERT Textbook - Biotechnology and its Applications NEET Notes | EduRev

Biology Class 12

Created by: Sushil Kumar

NEET : NCERT Textbook - Biotechnology and its Applications NEET Notes | EduRev

 Page 1


Biotechnology, as you would have learnt from the
previous chapter, essentially deals with industrial scale
production of biopharmaceuticals and biologicals using
genetically modified microbes, fungi, plants and animals.
The applications of biotechnology include therapeutics,
diagnostics, genetically modified crops for agriculture,
processed food, bioremediation, waste treatment, and
energy production. Three critical research areas of
biotechnology are:
(i) Providing the best catalyst in the form of improved
organism usually a microbe or pure enzyme.
(ii) Creating optimal conditions through engineering for
a catalyst to act, and
(iii) Downstream processing technologies to purify the
protein/organic compound.
Let us now learn how human beings have used
biotechnology to improve the quality of human life,
especially in the field of food production and health.
12.1 BIOTECHNOLOGICAL APPLICATIONS IN
AGRICULTURE
Let us take a look at the three options that can be thought
for increasing food production
(i) agro-chemical based agriculture;
CHAPTER 12
BIOTECHNOLOGY AND ITS
APPLICATIONS
12.1 Biotechnological
Applications in
Agriculture
12.2 Biotechnological
Applications in
Medicine
12.3 Transgenic Animals
12.4 Ethical Issues
2015-16
Page 2


Biotechnology, as you would have learnt from the
previous chapter, essentially deals with industrial scale
production of biopharmaceuticals and biologicals using
genetically modified microbes, fungi, plants and animals.
The applications of biotechnology include therapeutics,
diagnostics, genetically modified crops for agriculture,
processed food, bioremediation, waste treatment, and
energy production. Three critical research areas of
biotechnology are:
(i) Providing the best catalyst in the form of improved
organism usually a microbe or pure enzyme.
(ii) Creating optimal conditions through engineering for
a catalyst to act, and
(iii) Downstream processing technologies to purify the
protein/organic compound.
Let us now learn how human beings have used
biotechnology to improve the quality of human life,
especially in the field of food production and health.
12.1 BIOTECHNOLOGICAL APPLICATIONS IN
AGRICULTURE
Let us take a look at the three options that can be thought
for increasing food production
(i) agro-chemical based agriculture;
CHAPTER 12
BIOTECHNOLOGY AND ITS
APPLICATIONS
12.1 Biotechnological
Applications in
Agriculture
12.2 Biotechnological
Applications in
Medicine
12.3 Transgenic Animals
12.4 Ethical Issues
2015-16
208
BIOLOGY
(ii) organic agriculture; and
(iii) genetically engineered crop-based agriculture.
The Green Revolution succeeded in tripling the food supply but yet
it was not enough to feed the growing human population. Increased yields
have partly been due to the use of improved crop varieties, but mainly
due to the use of better management practices and use of agrochemicals
(fertilisers and pesticides). However, for farmers in the developing world,
agrochemicals are often too expensive, and further increases in yield with
existing varieties are not possible using conventional breeding. Is there
any alternative path that our understanding of genetics can show so that
farmers may obtain maximum yield from their fields? Is there a way to
minimise the use of fertilisers and chemicals so that their harmful effects
on the environment are reduced? Use of genetically modified crops is a
possible solution.
Plants, bacteria, fungi and animals whose genes have been altered by
manipulation are called Genetically Modified Organisms (GMO). GM
plants have been useful in many ways. Genetic modification has:
(i) made crops more tolerant to abiotic stresses (cold, drought, salt,
heat).
(ii) reduced reliance on chemical pesticides (pest-resistant crops).
(iii) helped to reduce post harvest losses.
(iv) increased efficiency of mineral usage by plants (this prevents early
exhaustion of fertility of soil).
(v) enhanced nutritional value of food, e.g., Vitamin ‘A’ enriched rice.
In addition to these uses, GM has been used to create tailor-made
plants to supply alternative resources to industries, in the form of starches,
fuels and pharmaceuticals.
Some of the applications of biotechnology in agriculture that you will
study in detail are the production of pest resistant plants, which could
decrease the amount of pesticide used. Bt toxin is produced by a
bacterium called Bacillus thuringiensis (Bt for short).  Bt toxin gene has
been cloned from the bacteria and been expressed in plants to provide
resistance to insects without the need for insecticides; in effect created a
bio-pesticide. Examples are Bt cotton, Bt corn, rice, tomato, potato and
soyabean etc.
Bt Cotton: Some strains of Bacillus thuringiensis produce proteins that
kill certain insects such as lepidopterans (tobacco budworm, armyworm),
coleopterans (beetles) and dipterans (flies, mosquitoes).  B. thuringiensis
forms protein crystals during a particular phase of their growth. These
crystals contain a toxic insecticidal protein. Why does this toxin not kill
the Bacillus? Actually, the Bt toxin protein exist as inactive protoxins but
once an insect ingest the inactive toxin, it is converted into an active form
of toxin due to the alkaline pH of the gut which solubilise the crystals.
The activated toxin binds to the surface of midgut epithelial cells and
2015-16
Page 3


Biotechnology, as you would have learnt from the
previous chapter, essentially deals with industrial scale
production of biopharmaceuticals and biologicals using
genetically modified microbes, fungi, plants and animals.
The applications of biotechnology include therapeutics,
diagnostics, genetically modified crops for agriculture,
processed food, bioremediation, waste treatment, and
energy production. Three critical research areas of
biotechnology are:
(i) Providing the best catalyst in the form of improved
organism usually a microbe or pure enzyme.
(ii) Creating optimal conditions through engineering for
a catalyst to act, and
(iii) Downstream processing technologies to purify the
protein/organic compound.
Let us now learn how human beings have used
biotechnology to improve the quality of human life,
especially in the field of food production and health.
12.1 BIOTECHNOLOGICAL APPLICATIONS IN
AGRICULTURE
Let us take a look at the three options that can be thought
for increasing food production
(i) agro-chemical based agriculture;
CHAPTER 12
BIOTECHNOLOGY AND ITS
APPLICATIONS
12.1 Biotechnological
Applications in
Agriculture
12.2 Biotechnological
Applications in
Medicine
12.3 Transgenic Animals
12.4 Ethical Issues
2015-16
208
BIOLOGY
(ii) organic agriculture; and
(iii) genetically engineered crop-based agriculture.
The Green Revolution succeeded in tripling the food supply but yet
it was not enough to feed the growing human population. Increased yields
have partly been due to the use of improved crop varieties, but mainly
due to the use of better management practices and use of agrochemicals
(fertilisers and pesticides). However, for farmers in the developing world,
agrochemicals are often too expensive, and further increases in yield with
existing varieties are not possible using conventional breeding. Is there
any alternative path that our understanding of genetics can show so that
farmers may obtain maximum yield from their fields? Is there a way to
minimise the use of fertilisers and chemicals so that their harmful effects
on the environment are reduced? Use of genetically modified crops is a
possible solution.
Plants, bacteria, fungi and animals whose genes have been altered by
manipulation are called Genetically Modified Organisms (GMO). GM
plants have been useful in many ways. Genetic modification has:
(i) made crops more tolerant to abiotic stresses (cold, drought, salt,
heat).
(ii) reduced reliance on chemical pesticides (pest-resistant crops).
(iii) helped to reduce post harvest losses.
(iv) increased efficiency of mineral usage by plants (this prevents early
exhaustion of fertility of soil).
(v) enhanced nutritional value of food, e.g., Vitamin ‘A’ enriched rice.
In addition to these uses, GM has been used to create tailor-made
plants to supply alternative resources to industries, in the form of starches,
fuels and pharmaceuticals.
Some of the applications of biotechnology in agriculture that you will
study in detail are the production of pest resistant plants, which could
decrease the amount of pesticide used. Bt toxin is produced by a
bacterium called Bacillus thuringiensis (Bt for short).  Bt toxin gene has
been cloned from the bacteria and been expressed in plants to provide
resistance to insects without the need for insecticides; in effect created a
bio-pesticide. Examples are Bt cotton, Bt corn, rice, tomato, potato and
soyabean etc.
Bt Cotton: Some strains of Bacillus thuringiensis produce proteins that
kill certain insects such as lepidopterans (tobacco budworm, armyworm),
coleopterans (beetles) and dipterans (flies, mosquitoes).  B. thuringiensis
forms protein crystals during a particular phase of their growth. These
crystals contain a toxic insecticidal protein. Why does this toxin not kill
the Bacillus? Actually, the Bt toxin protein exist as inactive protoxins but
once an insect ingest the inactive toxin, it is converted into an active form
of toxin due to the alkaline pH of the gut which solubilise the crystals.
The activated toxin binds to the surface of midgut epithelial cells and
2015-16
209
BIOTECHNOLOGY AND ITS APPLICATIONS
create pores that cause cell swelling and lysis and eventually cause death
of the insect.
Specific Bt toxin genes were isolated from Bacillus thuringiensis and
incorporated into the several crop plants such as cotton (Figure 12.1).
The choice of genes depends upon the crop and the targeted pest, as
most Bt toxins are insect-group specific. The toxin is coded by a gene
named cry. There are a number of them, for example, the proteins encoded
by the genes cryIAc and cryIIAb control the cotton bollworms, that of
cryIAb controls corn borer.
Figure 12.1 Cotton boll: (a) destroyed by bollworms; (b) a fully mature
cotton boll
(b)
(a)
Pest Resistant Plants: Several nematodes parasitise a wide variety of
plants and animals including human beings. A nematode Meloidegyne
incognitia infects the roots of tobacco plants and causes a great reduction
in yield. A novel strategy was adopted to prevent this infestation which
was based on the process of RNA interference (RNAi). RNAi takes place
in all eukaryotic organisms as a method of cellular defense. This method
involves silencing of a specific mRNA due to a complementary dsRNA
molecule that binds to and prevents translation of the mRNA (silencing).
The source of this  complementary RNA could be from an infection by
viruses having RNA genomes or mobile genetic elements (transposons)
that replicate via an RNA intermediate.
Using Agrobacterium vectors, nematode-specific genes were
introduced into the host plant (Figure 12.2). The introduction of DNA
was such that it produced both sense and anti-sense RNA in the host
cells. These two RNA’s being complementary to each other formed a double
stranded (dsRNA) that initiated RNAi and thus, silenced the specific mRNA
2015-16
Page 4


Biotechnology, as you would have learnt from the
previous chapter, essentially deals with industrial scale
production of biopharmaceuticals and biologicals using
genetically modified microbes, fungi, plants and animals.
The applications of biotechnology include therapeutics,
diagnostics, genetically modified crops for agriculture,
processed food, bioremediation, waste treatment, and
energy production. Three critical research areas of
biotechnology are:
(i) Providing the best catalyst in the form of improved
organism usually a microbe or pure enzyme.
(ii) Creating optimal conditions through engineering for
a catalyst to act, and
(iii) Downstream processing technologies to purify the
protein/organic compound.
Let us now learn how human beings have used
biotechnology to improve the quality of human life,
especially in the field of food production and health.
12.1 BIOTECHNOLOGICAL APPLICATIONS IN
AGRICULTURE
Let us take a look at the three options that can be thought
for increasing food production
(i) agro-chemical based agriculture;
CHAPTER 12
BIOTECHNOLOGY AND ITS
APPLICATIONS
12.1 Biotechnological
Applications in
Agriculture
12.2 Biotechnological
Applications in
Medicine
12.3 Transgenic Animals
12.4 Ethical Issues
2015-16
208
BIOLOGY
(ii) organic agriculture; and
(iii) genetically engineered crop-based agriculture.
The Green Revolution succeeded in tripling the food supply but yet
it was not enough to feed the growing human population. Increased yields
have partly been due to the use of improved crop varieties, but mainly
due to the use of better management practices and use of agrochemicals
(fertilisers and pesticides). However, for farmers in the developing world,
agrochemicals are often too expensive, and further increases in yield with
existing varieties are not possible using conventional breeding. Is there
any alternative path that our understanding of genetics can show so that
farmers may obtain maximum yield from their fields? Is there a way to
minimise the use of fertilisers and chemicals so that their harmful effects
on the environment are reduced? Use of genetically modified crops is a
possible solution.
Plants, bacteria, fungi and animals whose genes have been altered by
manipulation are called Genetically Modified Organisms (GMO). GM
plants have been useful in many ways. Genetic modification has:
(i) made crops more tolerant to abiotic stresses (cold, drought, salt,
heat).
(ii) reduced reliance on chemical pesticides (pest-resistant crops).
(iii) helped to reduce post harvest losses.
(iv) increased efficiency of mineral usage by plants (this prevents early
exhaustion of fertility of soil).
(v) enhanced nutritional value of food, e.g., Vitamin ‘A’ enriched rice.
In addition to these uses, GM has been used to create tailor-made
plants to supply alternative resources to industries, in the form of starches,
fuels and pharmaceuticals.
Some of the applications of biotechnology in agriculture that you will
study in detail are the production of pest resistant plants, which could
decrease the amount of pesticide used. Bt toxin is produced by a
bacterium called Bacillus thuringiensis (Bt for short).  Bt toxin gene has
been cloned from the bacteria and been expressed in plants to provide
resistance to insects without the need for insecticides; in effect created a
bio-pesticide. Examples are Bt cotton, Bt corn, rice, tomato, potato and
soyabean etc.
Bt Cotton: Some strains of Bacillus thuringiensis produce proteins that
kill certain insects such as lepidopterans (tobacco budworm, armyworm),
coleopterans (beetles) and dipterans (flies, mosquitoes).  B. thuringiensis
forms protein crystals during a particular phase of their growth. These
crystals contain a toxic insecticidal protein. Why does this toxin not kill
the Bacillus? Actually, the Bt toxin protein exist as inactive protoxins but
once an insect ingest the inactive toxin, it is converted into an active form
of toxin due to the alkaline pH of the gut which solubilise the crystals.
The activated toxin binds to the surface of midgut epithelial cells and
2015-16
209
BIOTECHNOLOGY AND ITS APPLICATIONS
create pores that cause cell swelling and lysis and eventually cause death
of the insect.
Specific Bt toxin genes were isolated from Bacillus thuringiensis and
incorporated into the several crop plants such as cotton (Figure 12.1).
The choice of genes depends upon the crop and the targeted pest, as
most Bt toxins are insect-group specific. The toxin is coded by a gene
named cry. There are a number of them, for example, the proteins encoded
by the genes cryIAc and cryIIAb control the cotton bollworms, that of
cryIAb controls corn borer.
Figure 12.1 Cotton boll: (a) destroyed by bollworms; (b) a fully mature
cotton boll
(b)
(a)
Pest Resistant Plants: Several nematodes parasitise a wide variety of
plants and animals including human beings. A nematode Meloidegyne
incognitia infects the roots of tobacco plants and causes a great reduction
in yield. A novel strategy was adopted to prevent this infestation which
was based on the process of RNA interference (RNAi). RNAi takes place
in all eukaryotic organisms as a method of cellular defense. This method
involves silencing of a specific mRNA due to a complementary dsRNA
molecule that binds to and prevents translation of the mRNA (silencing).
The source of this  complementary RNA could be from an infection by
viruses having RNA genomes or mobile genetic elements (transposons)
that replicate via an RNA intermediate.
Using Agrobacterium vectors, nematode-specific genes were
introduced into the host plant (Figure 12.2). The introduction of DNA
was such that it produced both sense and anti-sense RNA in the host
cells. These two RNA’s being complementary to each other formed a double
stranded (dsRNA) that initiated RNAi and thus, silenced the specific mRNA
2015-16
210
BIOLOGY
of the nematode. The consequence was that the parasite could not survive
in a transgenic host expressing specific interfering RNA. The transgenic
plant therefore got itself protected from the parasite (Figure 12.2).
Figure 12.2 Host plant-generated dsRNA triggers protection against nematode infestation:
(a) Roots of a typical control plants; (b) transgenic plant roots 5 days after deliberate
infection of nematode but protected through novel mechanism.
(a) (b)
12.2 BIOTECHNOLOGICAL APPLICATIONS IN MEDICINE
The recombinant DNA technological processes have made immense impact
in the area of healthcare by enabling mass production of safe and more
effective therapeutic drugs. Further, the recombinant therapeutics do not
induce unwanted immunological responses as is common in case of
similar products isolated from non-human sources. At present, about
30 recombinant therapeutics have been approved for human-use the
world over. In India, 12 of these are presently being marketed.
12.2.1 Genetically Engineered Insulin
Management of adult-onset diabetes is possible by taking insulin at
regular time intervals. What would a diabetic patient do if enough
human-insulin was not available? If you discuss this, you would soon
realise that one would have to isolate and use insulin from other animals.
Would the insulin isolated from other animals be just as effective as
that secreted by the human body itself and would it not elicit an immune
response in the human body? Now, imagine if bacterium were available
that could make human insulin. Suddenly the whole process becomes
so simple. You can easily grow a large quantity of the bacteria and make
as much insulin as you need.
Think about whether insulin can be orally administered to diabetic
people or not. Why?
2015-16
Page 5


Biotechnology, as you would have learnt from the
previous chapter, essentially deals with industrial scale
production of biopharmaceuticals and biologicals using
genetically modified microbes, fungi, plants and animals.
The applications of biotechnology include therapeutics,
diagnostics, genetically modified crops for agriculture,
processed food, bioremediation, waste treatment, and
energy production. Three critical research areas of
biotechnology are:
(i) Providing the best catalyst in the form of improved
organism usually a microbe or pure enzyme.
(ii) Creating optimal conditions through engineering for
a catalyst to act, and
(iii) Downstream processing technologies to purify the
protein/organic compound.
Let us now learn how human beings have used
biotechnology to improve the quality of human life,
especially in the field of food production and health.
12.1 BIOTECHNOLOGICAL APPLICATIONS IN
AGRICULTURE
Let us take a look at the three options that can be thought
for increasing food production
(i) agro-chemical based agriculture;
CHAPTER 12
BIOTECHNOLOGY AND ITS
APPLICATIONS
12.1 Biotechnological
Applications in
Agriculture
12.2 Biotechnological
Applications in
Medicine
12.3 Transgenic Animals
12.4 Ethical Issues
2015-16
208
BIOLOGY
(ii) organic agriculture; and
(iii) genetically engineered crop-based agriculture.
The Green Revolution succeeded in tripling the food supply but yet
it was not enough to feed the growing human population. Increased yields
have partly been due to the use of improved crop varieties, but mainly
due to the use of better management practices and use of agrochemicals
(fertilisers and pesticides). However, for farmers in the developing world,
agrochemicals are often too expensive, and further increases in yield with
existing varieties are not possible using conventional breeding. Is there
any alternative path that our understanding of genetics can show so that
farmers may obtain maximum yield from their fields? Is there a way to
minimise the use of fertilisers and chemicals so that their harmful effects
on the environment are reduced? Use of genetically modified crops is a
possible solution.
Plants, bacteria, fungi and animals whose genes have been altered by
manipulation are called Genetically Modified Organisms (GMO). GM
plants have been useful in many ways. Genetic modification has:
(i) made crops more tolerant to abiotic stresses (cold, drought, salt,
heat).
(ii) reduced reliance on chemical pesticides (pest-resistant crops).
(iii) helped to reduce post harvest losses.
(iv) increased efficiency of mineral usage by plants (this prevents early
exhaustion of fertility of soil).
(v) enhanced nutritional value of food, e.g., Vitamin ‘A’ enriched rice.
In addition to these uses, GM has been used to create tailor-made
plants to supply alternative resources to industries, in the form of starches,
fuels and pharmaceuticals.
Some of the applications of biotechnology in agriculture that you will
study in detail are the production of pest resistant plants, which could
decrease the amount of pesticide used. Bt toxin is produced by a
bacterium called Bacillus thuringiensis (Bt for short).  Bt toxin gene has
been cloned from the bacteria and been expressed in plants to provide
resistance to insects without the need for insecticides; in effect created a
bio-pesticide. Examples are Bt cotton, Bt corn, rice, tomato, potato and
soyabean etc.
Bt Cotton: Some strains of Bacillus thuringiensis produce proteins that
kill certain insects such as lepidopterans (tobacco budworm, armyworm),
coleopterans (beetles) and dipterans (flies, mosquitoes).  B. thuringiensis
forms protein crystals during a particular phase of their growth. These
crystals contain a toxic insecticidal protein. Why does this toxin not kill
the Bacillus? Actually, the Bt toxin protein exist as inactive protoxins but
once an insect ingest the inactive toxin, it is converted into an active form
of toxin due to the alkaline pH of the gut which solubilise the crystals.
The activated toxin binds to the surface of midgut epithelial cells and
2015-16
209
BIOTECHNOLOGY AND ITS APPLICATIONS
create pores that cause cell swelling and lysis and eventually cause death
of the insect.
Specific Bt toxin genes were isolated from Bacillus thuringiensis and
incorporated into the several crop plants such as cotton (Figure 12.1).
The choice of genes depends upon the crop and the targeted pest, as
most Bt toxins are insect-group specific. The toxin is coded by a gene
named cry. There are a number of them, for example, the proteins encoded
by the genes cryIAc and cryIIAb control the cotton bollworms, that of
cryIAb controls corn borer.
Figure 12.1 Cotton boll: (a) destroyed by bollworms; (b) a fully mature
cotton boll
(b)
(a)
Pest Resistant Plants: Several nematodes parasitise a wide variety of
plants and animals including human beings. A nematode Meloidegyne
incognitia infects the roots of tobacco plants and causes a great reduction
in yield. A novel strategy was adopted to prevent this infestation which
was based on the process of RNA interference (RNAi). RNAi takes place
in all eukaryotic organisms as a method of cellular defense. This method
involves silencing of a specific mRNA due to a complementary dsRNA
molecule that binds to and prevents translation of the mRNA (silencing).
The source of this  complementary RNA could be from an infection by
viruses having RNA genomes or mobile genetic elements (transposons)
that replicate via an RNA intermediate.
Using Agrobacterium vectors, nematode-specific genes were
introduced into the host plant (Figure 12.2). The introduction of DNA
was such that it produced both sense and anti-sense RNA in the host
cells. These two RNA’s being complementary to each other formed a double
stranded (dsRNA) that initiated RNAi and thus, silenced the specific mRNA
2015-16
210
BIOLOGY
of the nematode. The consequence was that the parasite could not survive
in a transgenic host expressing specific interfering RNA. The transgenic
plant therefore got itself protected from the parasite (Figure 12.2).
Figure 12.2 Host plant-generated dsRNA triggers protection against nematode infestation:
(a) Roots of a typical control plants; (b) transgenic plant roots 5 days after deliberate
infection of nematode but protected through novel mechanism.
(a) (b)
12.2 BIOTECHNOLOGICAL APPLICATIONS IN MEDICINE
The recombinant DNA technological processes have made immense impact
in the area of healthcare by enabling mass production of safe and more
effective therapeutic drugs. Further, the recombinant therapeutics do not
induce unwanted immunological responses as is common in case of
similar products isolated from non-human sources. At present, about
30 recombinant therapeutics have been approved for human-use the
world over. In India, 12 of these are presently being marketed.
12.2.1 Genetically Engineered Insulin
Management of adult-onset diabetes is possible by taking insulin at
regular time intervals. What would a diabetic patient do if enough
human-insulin was not available? If you discuss this, you would soon
realise that one would have to isolate and use insulin from other animals.
Would the insulin isolated from other animals be just as effective as
that secreted by the human body itself and would it not elicit an immune
response in the human body? Now, imagine if bacterium were available
that could make human insulin. Suddenly the whole process becomes
so simple. You can easily grow a large quantity of the bacteria and make
as much insulin as you need.
Think about whether insulin can be orally administered to diabetic
people or not. Why?
2015-16
211
BIOTECHNOLOGY AND ITS APPLICATIONS
Insulin used for diabetes was earlier extracted from
pancreas of slaughtered cattle and pigs. Insulin from an
animal source, though caused some patients to develop
allergy or other types of reactions to the foreign
protein. Insulin consists of two short polypeptide
chains: chain A and chain B, that are linked together by
disulphide bridges (Figure 12.3). In mammals, including
humans, insulin is synthesised as a pro-hormone (like a
pro-enzyme, the pro-hormone also needs to be processed
before it becomes a fully mature and functional hormone)
which contains an extra stretch called the C peptide.
This C peptide is not present in the mature insulin and is
removed during maturation into insulin.The main
challenge for production of insulin using rDNA techniques
was getting insulin assembled into a mature form. In
1983, Eli Lilly an American company prepared two DNA sequences
corresponding to A and B, chains of human insulin and introduced them
in plasmids of E. coli to produce insulin chains. Chains A and B were
produced separately, extracted and combined by creating disulfide bonds
to form human insulin.
12.2.2 Gene Therapy
If a person is born with a hereditary disease, can a corrective therapy
be taken for such a disease? Gene therapy is an attempt to do this.
Gene therapy is a collection of methods that allows correction of a
gene defect that has been diagnosed in a child/embryo. Here genes
are inserted into a person’s cells and tissues to treat a disease.
Correction of a genetic defect involves delivery of a normal gene into
the individual or embryo to take over the function of and compensate
for the non-functional gene.
The first clinical gene therapy was given in 1990 to a 4-year old girl
with adenosine deaminase (ADA) deficiency. This enzyme is crucial for
the immune system to function. The disorder is caused due to the deletion
of the gene for adenosine deaminase. In some children ADA deficiency
can be cured by bone marrow transplantation; in others it can be treated
by enzyme replacement therapy, in which functional ADA is given to the
patient by injection. But the problem with both of these approaches that
they are not completely curative. As a first step towards gene therapy,
lymphocytes from the blood of the patient are grown in a culture outside
the body. A functional ADA cDNA (using a retroviral vector) is then
introduced into these lymphocytes, which are  subsequently returned to
the patient. However, as these cells are not immortal, the patient requires
periodic infusion of such genetically engineered lymphocytes. However, if
the gene isolate from marrow cells producing ADA is introduced into cells
at early embryonic stages, it could be a permanent cure.
Figure 12.3Maturation of
pro-insulin into insulin
(simplified)
2015-16
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