Genetic engineering

Genetic Engineering: 

The movement of genes .from one organism to another is referred to as 'recombination DNA technology" or "Genetic Engineering". 

Gene transplantation

Tools for Genetic Engineering: 

Genetic donor Restriction endo nuclease Plasmids or Vectors Plasmids 

 The most commonly used vectors are "plasmids". Plasmids are small circular DNA molecules present in bacteria.

 Host: 

The bacteria are chosen-as host for cloning these genes. 

Cloning 

 Cloning means to make many similar copies of genes. Bacteria take the plasmid molecule and become 'recombinant microbe". The bacteria reproduce in large number of offspring each receiving a copy of gene. 
The transplanted gene expresses itself by making specific protein under its instruction. 
Mechanism 
 Plasmids are kept in solution containing the desired gene and endocnuclease. It will cut, open the plasmid ring and expose plasmid's sticky end. Now the complimentary free gene, will attach with open ends of plasmid by forming hydrogen bonds. 
Plasmid ring will close again, "Ligase" enzymes will serve as molecular glue and join the genes with plasmid. Now the plasmid becomes a recombination DNA, because DNA is now mixture of genetic material of two different organjsms. Determination of maleness by "SRY" gene.
 Isolation of vector from a bacterium Ligase , seals , ends ,Host's DNA Genetic Donor: Genes identified for specific protein are isolated in a tube from source DNA. Source of genetic material may be human, other' mammals or plants. "Source is called genetic donor". 

Restriction Endonuclease: 

 The donor DNA is cut by molecular scissors called "restriction enzymes" or "restriction endonuclease." Restriction endonuclease cut DNA, making some bases at the ends unpaired, that makes the ends sticky (searching for complimentary base). 

Source of Restriction Endonuclease:

 Restriction endonucleases are obtained from bacteria. 

Vectors or Plasmid: 

 "Vectors are carrier molecules for carrying the genes to a suitable host bacterium." 

 Applications of Genetic Engineering: 

Genetic engineering is so useful that several billion dollar industry is base on it. Some of its important applications are discussed below. 

Pharmaceuticals:

 Many medicines are prepared by this technique. For example, human insulin for diabetic persons, human growth hormone (HGH) for dwarf childrens, vaccines for hepatitis B and AIDS patients, and human interferon for cancer have successfully been made from bacteria. 

Gene Therapy

 This technique is given to cure patients of hereditary diseases like sickle-cell anaemia and haemophilia. To cure sickle-cell anaemic person, HbA gene is placed in bone marrow cells of sickle-cell anaemic person by a vector. The normal gene HbA starts forming its product and the patient becomes normal. 

Transgenic Animals: 

Transgenic animals are being made by introducing desired foreign genes into them. Transgenic animals are genetically designed to improve meat yield. Today transgenic sheep and goats are secreting human drugs in their milk e.g. Nancy and Ethel. 

Nancy(sheep): 

Nancy is a sheep that secrets human ATT in her milk. ATT cures emphysema - a respiratory disease.

 Ethel: 

Ethel is another sheep that secretes human factor VIII in her milk. Transgenic Plants: Herbicide resistant cotton and soyabean, pesticide resistant wheat, viral resistant rice and melon, fungus resistant corn, potatoes and tomatoes with built in insecticide have been made successful. 

Selective Breeding: 

Selective breeding is a practice to improve domesticated animals and plants. Individuals selected for breeding are those who have characteristics of our choice. These individuals kept on breeding and selecting individuals generation after generation till either we are satisfied with the product or no further improvement can be done. Example: Starting from a lean cow with very little milk, selective breeding was done in two directions. 
 (i) Most milk 
(ii) . Most meat One group of cattle breeders ended with large size modern beef cow with meat enough for lots of Kababs, steaks and roasts. The other group ended with modern dairy cow with lots of milk. 

Hybridization and Selective Breeding:

 Hybridization and selective breeding have produced large number of improved varieties of animals and plants. 

Neeli 

Neeli is the famous breed of buffalo selected for centuries in the areas of Punjab, where river Sutlej flows. Ravi is the best breed of Ravi areas of Punjab. Their natural hybridization in areas of the common belt of the two rivers Okara has resulted into famous cross breed Neeli Ravi. Rahu and Thaila Rahu and Thaila are the two major carps of our rivers famous for their delicious white meat. Rahu- Thaila hybrid combines the superior taste of Rahu with larger size and faster growth rate of thaila. 
Some other examples Jersey-Sahiwal cow, Dhani ox, Kajli sheep, Layer chicken, Maxipak wheat and Super Kernel Basmati rice are some other examples of hybridization and Selective breeding process. But it is very slow process. It takes months and even years to raise a few generations of animals and plans.