dna recombinant technology (1)
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DNA recombinant
technology
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A series of procedures used to
recombine DNA segments.. Under certain conditions, a recombinant DNA
molecule can enter a cell and replicate.
Definition of recombinant DNAtechnology()
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History of recombinant DNA
technology
Recombinant DNA technology is one
of the recent advances inbiotechnology, which was developedby two scientists named Boyer and
Cohen in 1973.
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Basic principle of recombinant
DNA technology
The DNA is inserted into another
DNA molecule called µvector¶()
. The recombinant vector is then
introduced into a host cell where itreplicates itself, the gene is thenproduced
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Basic principle of recombinant
DNA technology
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Applications of
Recombinant DNATechnologyLarge-scale production of humanproteins by geneticallyengineered bacteria.
Such as : insulin, Growth
hormone, Interferons andBlood clotting factors (VIII & IX)
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Production of Human
Insulin() 1) Obtaining the human insulin geneHuman insulin gene can be obtained bymaking a complementary DNA (cDNA) copyof the messenger RNA (mRNA) for human
insulin.
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2)Joining the human insulin geneinto a plasmid() vector
The bacterial plasmids and the cDNA aremixed together. The human insulin gene
(cDNA) is inserted into the plasmid throughcomplementary base pairing at sticky ends.
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3)Introducing the recombinantDNA plasmids into bacteria
The bacteria E.coli is used as the host cell. If E.
coli and the recombinant plasmids are mixedtogether in a test-tube.
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4)Selecting the bacteria whichhave taken up the correct
piece of DNAThe bacteria are spread onto nutrient agar. Theagar also contains substances such as anantibiotic which allows growth of only the
transformed bacteria.
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Vaccinedevelopment (
)The surface antigen of Plasmodium
falciparum, one of the 4 species of malaria
has been transferred to E. coli to produceamounts large enough to develop a vaccine
against this form of malaria(). It
works well enough for people who will
visit a malarious region for a relativelyshort period of time
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Hemophilia() A andB
The genes encoding factors 8 and 9 are on the X chromosome.
Like other X-linked disorders, hemophilia A and B are foundalmost exclusively in males because they inherit just a singleX chromosome, and if the gene for factor 8 (or 9) on it isdefective, they will suffer from the disease.
There are many different mutant versions of the genes forfactors 8 and 9. Although some produce only a minor effect on the function of their protein, others fail to produce anyfunctioning clotting factor.
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Treating Hemophilia A and B
Factor 8 and 9 can be extracted from donated blood, usually
pooled from several thousand donors, and purified. Injections of
this material can halt episodes of bleeding in hemophiliacs and
have allowed countless young men to live relatively normal lives.However, blood contaminated with the human immunodeficiency
virus (HIV) was unknowingly used to manufacture preparations of
factors 8 and 9. Many have since died of AIDS.
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The Future of Treating Hemophilia Aand B
all donated blood is now tested to see if thedonor has been infected with HIV (as well ashepatitis B and C);
plasma-derived preparations of factors 8 and 9are now treated with heat and/or solvents todestroy any viruses that might be present ;
recombinant factor 8 and recombinant
factor 9 made by genetic engineering are nowavailable.
Now the treatment become more safety!
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Still in the experimental stages, it may be possible totransfer the gene for normal adult hemoglobin intomarrow stem cells of an individual with sickle-cell
anemia(). The goal is to promote thegrowth of enough cells to produce enough normalhemoglobin to alleviate the symptoms of sickle-cellanemia. One hundred percent (100%) is NOT required to attain the alleviation of symptoms.
Gene therapy for genetic diseases
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Safety Issues in relation to
Recombinant DNA TechnologyAs bacteria is commonly used in recombinant DNA work,there has always been a concern among scientists and aworry among people that there is a possibility that a clone
of highly pathogenic recombinant bacteria were made byaccident, then escaped from the laboratory and caused anepidemic for which no drugs were available.
Recombinant DNA Advisory Committee (RAC) wasestablished in 1974 in the United States, whichresponds to public concerns regarding the safety of manipulation of genetic material through the use of recombinant DNA techniques.
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2 types of control : physical
containment and biologicalcontainment ()
Effective biological safety programs were
operated in a variety of laboratories, whichinclude a set of standard practices generallyused in microbiological laboratories, andspecial procedures, equipment and laboratoryinstallations that provide physical barriers of varying degrees.
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In considering biological containment, thevector (plasmid, organelle, or virus) for therecombinant DNA and the host (bacterial,plant, or animal cell) in which the vector ispropagated in the laboratory will be consideredtogether.
(i) survival of the vector in its host outside the
laboratory, and (ii) transmission of the vectorfrom the propagation host to other non-laboratory hosts.
Biological containment
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Dangerous of DNArecombinant technology
It is always possible that anantibiotic-resistant plasmid could beaccidentally incorporated into adangerous pathogen with seriousmedical consequences.
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http://www.ied.edu.hk/biotech/eng/classrm/explain/gene5.htm