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Submitted by;
Labhesh Parakh
1st
Year BSc. Biotechnology
Faculty of Life Sciences (JSS AHER)
Submitted to;
DR. SHASHANKA K. PRASAD
Assistant Professor
Dept. of BIOTECHNOLOGY & BIOINFORMATICS
Faculty of Life Sciences
JSS Academy of Higher Education & Research
(JSS AHER)
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INTRODUCTION
Recombinant DNA, molecules of DNA from
two different species that are inserted into a host
organism to produce new genetic combinations
that are of value to science, medicine, agriculture,
and industry. Since the focus of all genetics is the
gene, the fundamental goal of laboratory
geneticists is to isolate, characterize, and
manipulate genes. Although it is relatively easy to
isolate a sample of DNA from a collection of cells,
finding a specific gene within this DNA sample
can be compared to finding a needle in a
haystack.
➢ Consider the fact that each human cell contains
approximately 2 meters (6 feet) of DNA.
Therefore, a small tissue sample will contain many
kilometers of DNA. However, recombinant DNA
technology has made it possible to isolate one
gene or any other segment of DNA, enabling
researchers to determine its nucleotide sequence,
study its transcripts, mutate it in highly specific
ways, and reinsert the modified sequence into a
living organism.
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In biology a clone is a group of individual cells or
organisms descended from one progenitor. This
means that the members of a clone are genetically
identical, because cell replication produces identical
daughter cells each time. The use of the word clone
has been extended to recombinant DNA technology,
which has provided scientists with the ability to
produce many copies of a single fragment of DNA,
such as a gene, creating identical copies that
constitute a DNA clone. In practice the procedure is
carried out by inserting a DNA fragment into a small
DNA molecule and then allowing this molecule to
replicate inside a simple living cell such as a
bacterium. The small replicating molecule is called a
DNA vector (carrier). The most commonly used
vectors are plasmids (circular DNA molecules that
originated from bacteria), viruses, and yeast cells.
Plasmids are not a part of the main cellular genome,
but they can carry genes that provide the host cell
with useful properties, such as drug resistance,
mating ability, and toxin production. They are small
enough to be conveniently manipulated
experimentally, and, furthermore, they will carry
extra DNA that is spliced into them.
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DNA Sequencing
Once a segment of DNA has been cloned, its nucleotide
sequence can be determined. The nucleotide sequence is
the most fundamental level of knowledge of a gene or
genome. It is the blueprint that contains the instructions
for building an organism, and no understanding of
genetic function or evolution could be complete without
obtaining this information.
The two basic sequencing approaches are😊
The Maxam-Gilbert method, discovered by and
named for American molecular biologists Allan M.
Maxam and Walter Gilbert.
The Sanger method, discovered by English
biochemist Frederick Sanger.
In the , The Sanger method,
DNA chains are synthesized on a template strand, but
chain growth is stopped when one of four possible
dideoxy nucleotides, which lack a 3′ hydroxyl group, is
incorporated, thereby preventing the addition of another
nucleotide. A population of nested,
truncated results that represents each of
the sites of that particular nucleotide in the template DNA.
These molecules are separated in a procedure
called , and the inferred nucleotide
sequence is deduced using a computer.
Frederick Sanger
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Genetically Modified
Organisms (GMOs)
The ability to obtain specific DNA clones by using
recombinant DNA technology has made it possible to add
the DNA of one organism to the genome of another. The
added gene is called a transgene. The transgene inserts
itself into a chromosome and is passed to the progeny as a
new component of the genome. The resulting organism
carrying the transgene is called a transgenic organism or a
genetically engineered organism (GEO). In this way, a
“designer organism” is made that contains some specific
change required for an experiment in basic genetics or for
improvement of some commercial strain. Several transgenic
plants have been produced. Genes for toxins that kill insects
have been introduced in several species, including corn and
cotton. Bacterial genes that confer resistance to herbicides
also have been introduced into crop plants. Other plant
transgenes aim at improving the nutritional value of the
plant.
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Gene therapy is the introduction of a
normal gene into an individual’s genome in
order to repair a mutation that causes a
genetic disease. When a normal gene is
inserted into a mutant nucleus, it most
likely will integrate into a chromosomal
site different from the defective allele;
although this may repair the mutation, a
new mutation may result if the normal
gene integrates into another functional
gene. If the normal gene replaces the
mutant allele, there is a chance that the
transformed cells will proliferate and
produce enough normal gene product for
the entire body to be restored to the un-
diseased phenotype. So far, human gene
therapy has been attempted only on
somatic (body) cells for diseases such as
cancer and severe combined
immunodeficiency syndrome (SCIDS).
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Somatic cells cured by gene therapy may
reverse the symptoms of disease in the
treated individual, but the modification is
not passed on to the next generation.
Germinal gene therapy aims to place
corrected cells inside the germ line (e.g.,
cells of the ovary or testis). If this is
achieved, these cells will undergo meiosis
and provide a normal gametic contribution
to the next generation. Germinal gene
therapy has been achieved experimentally
in animals but not in humans.
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Recombinant DNA technology has led to powerful
diagnostic procedures useful in both medicine and
forensics.
➢ In medicine these diagnostic procedures are
used in counselling prospective parents as to
the likelihood of having a child with a
particular disease, and they are also used in
the prenatal prediction of genetic disease in
the foetus.
➢ Researchers look for specific DNA fragments
that are located in close proximity to the gene
that causes the disease of concern.
➢ These fragments, called restriction fragment
length polymorphisms (RFLPs), often serve as
effective “genetic markers.”
➢ In forensics, DNA fragments called variable
number tandem repeats (VNTRs), which are
highly variable between individuals, are
employed to produce what is called a “DNA
fingerprint.”
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➢ A DNA fingerprint can be used to determine if
blood or other body fluids left at the scene of
a crime belongs to a suspect.
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➢ Recombinant DNA technology is an important
development in science that has made the
human life much easier. In recent years, it has
advanced strategies for biomedical
applications such as cancer treatment, genetic
disorders, diabetes and several plant
disorders especially viral and fungal
resistance.
➢ Today, recombinant proteins & other
products that are being processed with the
use of r-DNA technology are found in
essentially every western pharmacy, doctor’s
or veterinarian’s office, Medical testing
laboratory & Biological research laboratory.
✓ https://en.wikipedia.org/wiki/Recombinant_DNA
✓ https://www.britannica.com/science/recombinant-DNA-
technology
✓ NCERT Biology – 12
