Genetic engineering

Introduction and application of genetic engineering

Genetic engineering

Genetic engineering, the artificial manipulation, modification, and recombination of DNA or other nucleic acid molecules in order to modify an organism or population of organisms.

The term genetic engineering initially referred to various techniques used for the modification or manipulation of organisms through the processes of heredity and reproduction. As such, the term embraced both artificial selection and all the interventions of biomedical techniques, among them artificial insemination, in vitro fertilization (e.g., “test-tube” babies), cloning, and gene manipulation. In the latter part of the 20th century, however, the term came to refer more specifically to methods of recombinant DNA technology (or gene cloning), in which DNA molecules from two or more sources are combined either within cells or in vitro and are then inserted into host organisms in which they are able to propagate.

The possibility for recombinant DNA technology emerged with the discovery of restriction enzymes in 1968 by Swiss microbiologist Werner Arber. The following year American microbiologist Hamilton O. Smith purified so-called type II restriction enzymes, which were found to be essential to genetic engineering for their ability to cleave a specific site within the DNA (as opposed to type I restriction enzymes, which cleave DNA at random sites). Drawing on Smith’s work, American molecular biologist Daniel Nathans helped advance the technique of DNA recombination in 1970–71 and demonstrated that type II enzymes could be useful in genetic studies. Genetic engineering based on recombination was pioneered in 1973 by American biochemists Stanley N. Cohen and Herbert W. Boyer, who were among the first to cut DNA into fragments, rejoin different fragments, and insert the new genes into E. coli bacteria, which then reproduced.

Process And Techniques

Most recombinant DNA technology involves the insertion of foreign genes into the plasmids of common laboratory strains of bacteria. Plasmids are small rings of DNA; they are not part of the bacterium’s chromosome (the main repository of the organism’s genetic information). Nonetheless, they are capable of directing protein synthesis, and, like chromosomal DNA, they are reproduced and passed on to the bacterium’s progeny. Thus, by incorporating foreign DNA (for example, a mammalian gene) into a bacterium, researchers can obtain an almost limitless number of copies of the inserted gene. Furthermore, if the inserted gene is operative (i.e., if it directs protein synthesis), the modified bacterium will produce the protein specified by the foreign DNA.

A subsequent generation of genetic engineering techniques that emerged in the early 21st century centred on gene editing. Gene editing, based on a technology known as CRISPR-Cas9, allows researchers to customize a living organism’s genetic sequence by making very specific changes to its DNA. Gene editing has a wide array of applications, being used for the genetic modification of crop plants and livestock and of laboratory model organisms (e.g., mice). The correction of genetic errors associated with disease in animals suggests that gene editing has potential applications in gene therapy for humans.

Applications Genetic engineering

Animal Husbandry

Neither the use of animal vaccines nor adding bovine growth hormones to cows to dramatically increase milk production can match the real excitement in animal husbandry: transgenic animals and clones.  Transgenic animals model advancements in DNA technology in their development. The mechanism for creating one can be described in three steps:

  • Healthy egg cells are removed from a female of the host animal and fertilized in the laboratory.
  • The desired gene from another species is identified, isolated, and cloned.
  • The cloned genes are injected directly into the eggs, which are then surgically implanted in the host female, where the embryo undergoes a normal development process.

 

Control of Oil Pollution

Oil spills from oil tankers either on water or water sur­faces cause a major environmental hazard. Earlier use of chemical dispersants was shown to cause major pollution in shallow water due to their toxic nature and prolong persistence in the environment.

Various species of Pseudomonas have the property to consume available hydrocarbons from oil and can produce active surface compounds that can emulsify oil in water and thus facili­tate easy removal of oil. Dr. Ananda Chakrobarty has engineered a strain of Pseudomonas aeruginosa which produces a glycolipid emulsifier that reduces the surface tension of an oil-water interface and thus helps in removal of oil from water.

Many such genetically engineered microbes can be used by mixing with straw, which then will be scattered over the spilled oil, the straw will first soak oily water and then the microbes will break up the oil into non-toxic, non-polluting substances, rende­ring the environment harmless.

Control of Heavy Metal Pollution

Integrated management of polluted ecosys­tem by the use of diverse kind of organisms which restore the natural process in the ecosystem is called bioremediation. Appli­cation of genetically engineered organisms, specially plants in bioremediation, to rid con­taminated soil from heavy metal toxicity has proved encouraging.

Use of Bio-Pesticides

In developing countries, about 60 to 70% of food, during harvesting and post-harvested period is lost on account of pests. Majority of chemical pes­ticides, herbicides and fertilisers cause numerous hazards, because these substances release various pollutants in the environment. To minimise the use of chemicals and pesti­cides, bio-pesticides are being used.

These are compounds derived from natural biological sources like animals, plants; bacteria and can limit the growth of pests. For example, plant-incorporated protectants (PIPs) are bio-pesticides produced by plants through genetic manipulation.

Medicine

Genetic engineering has resulted in a series of medical products. The first two commercially prepared products from recombinant DNA technology were insulin and human growth hormone, both of which were cultured in the E. coli bacteria. Since then a plethora of products have appeared on the market, including the following abbreviated list, all made in E. coli:

  • Tumor necrosis factor. Treatment for certain tumor cells
  • Interleukin-2 (IL-2). Cancer treatment, immune deficiency, and HIV infection treatment
  • Treatment for heart attacks Taxol.
  • Treatment for ovarian cancer Interferon. Treatment for cancer and viral infections

In addition, a number of vaccines are now commercially prepared from recombinant hosts. At one time vaccines were made by denaturing the disease and then injecting it into humans with the hope that it would activate their immune system to fight future intrusions by that invader. Unfortunately, the patient sometimes still ended up with the disease.

Agriculture

Crop plants have been and continue to be the focus of biotechnology as efforts are made to improve yield and profitability by improving crop resistance to insects and certain herbicides and delaying ripening (for better transport and spoilage resistance). The creation of a transgenic plant, one that has received genes from another organism, proved more difficult than animals. Unlike animals, finding a vector for plants proved to be difficult until the isolation of the Ti plasmid, harvested from a tumor-inducing (Ti) bacteria found in the soil. The plasmid is “shot” into a cell, where the plasmid readily attaches to the plant’s DNA. Although successful in fruits and vegetables, the Ti plasmid has generated limited success in grain crops.

Creating a crop that is resistant to a specific herbicide proved to be a success because the herbicide eliminated weed competition from the crop plant. Researchers discovered herbicide-resistant bacteria, isolated the genes responsible for the condition, and “shot” them into a crop plant, which then proved to be resistant to that herbicide. Similarly, insect-resistant plants are becoming available as researchers discover bacterial enzymes that destroy or immobilize unwanted herbivores, and others that increase nitrogen fixation in the soil for use by plants.

Geneticists are on the threshold of a major agricultural breakthrough. All plants need nitrogen to grow. In fact, nitrogen is one of the three most important nutrients a plant requires. Although the atmosphere is approximately 78 percent nitrogen, it is in a form that is unusable to plants. However, a naturally occurring rhizobium bacterium is found in the soil and converts atmospheric nitrogen into a form usable by plants. These nitrogen-fixing bacteria are also found naturally occurring in the legumes of certain plants such as soybeans and peanuts. Because they contain these unusual bacteria, they can grow in nitrogen-deficient soil that prohibits the growth of other crop plants. Researchers hope that by isolating these bacteria, they can identify the DNA segment that codes for nitrogen fixation, remove the segment, and insert it into the DNA of a profitable cash crop! In so doing, the new transgenic crop plants could live in new fringe territories, which are areas normally not suitable for their growth, and grow in current locations without the addition of costly fertilizers.

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