Genetic Engineering explained in detail


Genetic Engineering:
Defination:
        Use of experiment techniques to produce DNA molecules containing new genes or new combinations of genes is termed as genetic engineering.
                                             OR
Genetic engineering aims at synthesizing recombinant DNA which contains DNA from different sources.
Objectives of genetic engineering:
1.Production of varieties of plants and animals having desirable organisms. 
2:Attempts to repair genes for various purposes as gene therapy.
3:Manipulation of gene for industrial and commercial products.
4:Treatment of genetic defects in higher organisms.
5:To help in overcoming pollution and other environmental problems.
Basic GE techniques
There are two basic genetic engineering techniques as
1:Recombinant DNA technology.
2:DNA cloning.
1. Recombinant DNA Technology :-
It is based on three biological tools which are :-
i.            Restriction Enzymes:
To cut the selected DNA of our choice from a donor organisms.
ii.         Vector :
Is a transfer agent which allows recombinant DNA to enter a cell and replicates.
iii.       Host Organisms or genetically modified organism (GMO):
         Is the target host which then becomes a GMO.
Mechanism :
                                                            Recombinant DNA technology involves following steps.
1.Isoloation or Cutting of gene of interest :
Gene of interest is cutted with the help of a group of bacterial enzymes called Restriction enzymes. In nature, these enzymes protect bacteria against viruses or other bacterial cells .Hundreds of restriction enzymes are been identified. Some are :
i.         Eco R1 :
This restriction enzymes is obtained from E.coli bacteria.
ii.       Hind III :
It is obtained from bacteria Hemophilus influenzae .
iii.    Hae III :
It is obtained from bacteria hemophilus aegytus.
                                                        These Enzymes cut the DNA of the donor organism at specific side where gene of interest is located . They cut the DNA and made sticky ends. Which are able to reattach to its complementary sequence at the end of any DNA molecule that has been cut by the same restriction enzyme.




à Same Enzymes cut DNA with in or near their particular recognition sequences. These sequences are mostly four to six nucleotides and always symmetrical. Such sequences are called “Pallindromes
à Enzymes which cut DNA into sticky ends, They can pair with eachother and rejoin easily by DNA ligase (Joining enzymes )
Examples: ECO R1, HIND III.
Those enzymes cut DNA into blunt ends which are difficult to attach and rejoin.
2. Insertion of gene of interest in vector :
In this step DNA fragments called Restriction Fragments are combined with vector and transferred to the host organism. Some types of vectors are:
i.                  Plasmids : These are extra chromosomal DNA present in many bacteria. It is able to contain, Divide and grow into millions with DNA of two different sources, A donor and a bacterium.
ii.               Viruses : These follow the infection, integrate into chromosome and delivers recombinant DNA directly to a chromosome
Example : Retro Viruses are particularly  used as vectors.
iii.               Cosmids : These are synthetic vectors and are used for addition sticky ends by changing blunt ends into sticky ends.
                           3.  Transfer and growth of recombinant DNA into GMO :
                            In  this step the isolated gene of interest and plasmid are attacked according to their complementary sequences. Now this organism containing recombinant DNA called as GMO. These are provided then by a suitable medium where they grow and result in increase number of cells,all making copies of the same recombinant DNA called DNA CLONES or GENE CLONES.
                       4. Expression of gene :
                Expression of gene of interest take place by the formation of mRNA which is translated into proteins.
         
DNA CLONING :
                                    Definition :- Production of many identical copies of gene of interest is called as GENE CLONING or DNA CLONING .
                          Sources of genes for cloning :
                                               There are two sources of genes for cloning.
1:Genomic liberaries:
                                   In this DNA is isolated directly from an organism. In genomic library ,large number of bacterial on phage clones are present.Each one of them contain its own DNA and DNA segment of a foreign genome.
                                              Later on entire DNA from the cells of an organism with gene of interest and also plasmids from bacteria all are isolated.Then recombinant DNA are allowed to clone which results into thousands of clones of plasmid which give rise to genomic library.

2:Complimentary DNA library or cDNA:
                                   In eukaryotic genes oftan contains long non-coding regions called introns,which are unable to express by bacterial cells.For solving this problem scientists made an artificial gene with no introns.
                                            A double standard DNA molecule carrying the coding sequence of gene but no interon is called complimentary DNA or cDNA.
Mechanism:
1:m RNA molecule is isolated and used as a template to synthesize first complementary DNA strand.
2:Enzyme reverse transcriptase is used to catalyzed the synthesis.
3:Then RNA is now degraded and second DNA strand is made using DNA polymerase and first strand of DNA as template.
4:Now both strands are formed of double stranded molecule of complementary DNA or cDNA.
5:This cDNA is able to translate and transcribed by bacterial cell.
Cloning of gene:
                           In laboratory ,cloning of gene is done by the process of PCR.PCR is
                                                                   It is a technique by which any piece of DNA can be quickly amplified in vitro.DNA is incubated under appropriate conditions with the enzyme DNA polymerase and special short pieces of nucleic acid called primers.
Mechanism of polymerase chain reaction:
     For this reaction following material is required .
1:Double  stranded DNA containing nucleotide sequences .
2:DNA polymerase enzyme.
3:All four nucleotides required to form a new DNA.
4:Primers which are required for initiation of DNA polymerase enzyme to synthesize DNA.
Primers are short pieces of nucleic acid and particular primers used in PCR are chemically synthesized.
Procedure:
1.DNA is briefly heated to separate the strands
2.Mixture of DNA polymerase, all four nucleotides and primers is allowed to cool so that primers may bind to the ends of target sequence by hydrogen bonds, one primer on each strand.
3.DNA polymerase extends the primers by adding nucleotides using the longer DNA strands as templates. Within a short time ( about 5 minutes ) the amount of target DNA is doubled.
4.Solution is heated again, starting another cycle of strand separation, primer binding and DNA synthesis.
4.DNA cloning or gene cloning can be done more efficiently by using electrophroesis, nucleic and hybridization and RELP analysis,
Applications of Genetic Engineering :
1.Marvellous Medicines :-
àHuman Insulin gene was produced by E.Coli bacteria. It was the first geneticall engineered protein.
àIn 1977, E.coli bacterium was created that was capable of synthesizing the human growth hormone.
àBy genetically modified microorganism, another hormone thymosin produced which is used against lungs and brain cancer.
àBy genetically modified techniques ,a pain killer Beta-Endorphin is produced
àVaccines against hepatitis B and foot and mouth disease of cattle, goat & deer ( viral disease ) are being produced genetic engineering.
àInterferons  are anti-viral proteins which are first time produced in 1980 by genetic engineering .
àDue to genetically engineered microorganism, a enzyme unrokinase is produced which is used to dissolve blood clots.
    2.Cure to heredity diseases :
                                                                          Genetic engineering techniques can also be used to cure blood disease Like  thalaesemia  & Sickle_Cell anaemia which are unherited disease. These diseases are result from defects in single gene and is cured by transforming these genes with normal ones.
                                                   Now it has become possible to modify genes in human egg cell which can lead to the elimination of inherited diseases like haemophila
   3.Tes tube babies :
                                                                          Fertilization of human egg outside the human body in vitro condition test tube babies. First attempt to produce test tube baby us done by Italian scientist Dr.Petruca in 1959.
                                                    First test tube baby girl on 25     th of July 1978  “Louis Joy Brown” Was born as a gift of genetic engineering.
   4.Solution to infertility :
                                                                         Studies shows that infertility rate both in man and women is growing in whole come this problem.
                                                      Female infertility can also be cured at different levels by procedures and medicines.
    5.Superior Baby :
                                                  It is now possible to make RNA molecule and develop whole new genetic code in lab. So it may be quite possible that in future, baby can be produced having all the physical & intellectual. Such babies are called superior babies.
    6.Agricultural Boosts :
                                                                            Genetic engineering is providing one of the most important means by which crop plants will be improved in the future. 
àPathogen-free plants are now produced which have virus –free particals along their meristems culture which means increased yield of crops. Example: Potato
àGenetic Engineering able to fuse protoplasts of two different plants and produce a somatic hybrid cell. Such hybrids are produced in tobacco, petunia and carrot. Mostly hybrids are sterile. But some are fertile as “Pomate” which is a somatic hybrid between the species of potato and tomato.This hybrid conatains potatoes on roots and tomatoes on branches.
àInsecticide Resistance in plants is another miracle of gentic engineering BT gene ( a gene from bacterium bacillus thuringeinsis ) has been transformed to plants . This gene produces a toxin which kills butterfly & moth larvae on their first bite. Those plants which are with BT gene are called as BT PLANTS is a example of such plants which resists damage caused by chewing insects.
àAttempts are being made to increase the availability of nitrogen, a limiting factor in crop production, by transferring genes responsible for nitrogen fixation into crops such as wheat, maize, which do not fix nitrogen.
àHerbicide Resistance in plants can be engineered by transferring a mutant gene from bacterium Salmonella into plant that were resistant to the herbicide.
àGenetic engineering is now able to transfer genes of drought resistance to normal plants, making them able to control water loss. It will help to reduce the needed amount of water for irrigation. Desert petunia genes for drought resistance are transferred to normal petunia which results 40% less water requirement.
àGenetically altered forms of Ethylene receptor gene ( etr 1-1 ) transfer into tomatoes and remain golden colour for 100 days after picking whereas untreated fruits starts to turn deep red and begin to rot in few days . Same gene transfer to petunia plants increase the longevity of flowering and made them viable 8 days of great interest in cut-flower industry.
àAlteration in fatty acid and biosynthetic  pathways help to reduce proportion of saturated fats in soy bean and canola and results in more oil production from the.
àA modified “ice-minus” strain of bacterium Pseudomonas Syringa had been developed to reduce the chances of certain crops to frost ( dying of plants on temperature below the freezing pint ). Therefore now plants are allow to plant early.
7. Elimination of Pollutants :
                                                                         Genetic Engineering helps to make such microbes which decomposes or degraded the poisonous compounds and results in controlling the pollution.
8. Industrial revolution :
      àGenetic Engineering have created oil producing microorganisms that generates organic compounds which are equivalent to Petroleum .
     àvaluable fuel like ethanol methane have been obtained through genetically engineered microbes
     àGene Transfer is also being used to produce desirable products that plants do not normally make . Possibilities rang from the production of pharmaceutical proteins such as vaccines  to the production of polyhydroxybutanol ( a compound used to make plastic )
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Risks of Genetic Engineering :
                                                                                      No doubt genetic engineering has many beneficial effect but it also give great threat to humanity. It has raise many many moral, thical and legal questions _
àGenetic engineering may introduce genes of viral cancer which can be used as biological weapons  in war.
àThere is also a great fear that genetic engineering may lead to a new world full of harmful creatures
àDrug resistance genes can also be produced. Hybrid of such kind which have gene of poison including  snake gernome can also be produced.
àWhen there would be exact copies ally produced individuals, then who would be the father or mother. It will also create the problems of property and inheritance.   
                  <==Hope this article broaden your vision==>
                                   <--Thanks For Reading-->
       




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