Genetic Engineering Outline,DNA Molecules,Restriction Endonucleases,Cloning Vehicles,Human Insulin

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Home >> Plant Genetic Engineering Introduction >> Plant Genetic Engineering Introduction

Plant Genetic Engineering Introduction
Genetic Engineering Outline
Animal Viruses
Detection and Selection of Coned Genes

	Genetic Engineering Outline - Understanding genetic engineering requires two types of knowledge, namely, a grasp of the concepts of molecular biology and familiarity with laboratory manipulations. The first step is to break open living cells. A number of methods are available for accomplishing this. One popular way is to shear the cells in a blender and then treat them with a detergent. The next step is to remove genetic information from them. This is a fairly easy, straightforward process because the information is stored in a chemical form as part of DNA.
Since DNA molecules are thousands of times longer than most other large molecules found in cells, it has been possible to develop techniques of purifying DNA. The DNA molecules are spooled onto a glass rod. The glass rod bearing the DNA molecules is then lifted out of the mixture of broken cells. The third step is to cut specific genes of interest away from the rest of the DNA. DNA is divided into segments which correspond to the letters in the genetic code. When a number of segments or genetic letters are organized in a specific combination, they create a gene. The molecular scissors used to cut DNA into gene size pieces are called restriction endonucleases; they recognize and cut at specific DNA sequences.
The next step is to splice (join) these specific sections of DNA into agents called cloning vehicles (such as phages, plasmids etc.) that carry the DNA sections into other living cells. Cloning vehicles are relatively short DNA molecules that can penetrate the wall of a living cell and can multiply inside that cell. The splicing process produces a chimeric DNA molecule containing part of the specific gene and part of the cloning vehicle. Such a DNA molecule is also called a recombinant DNA molecule. Once a foreign gene has been spliced into a cloning vehicle, both the vehicle and the foreign gene are transferred into a cell that is normally a host for the vehicle. Usually the host cells are single-celled organisms such as bacteria or yeast. The final step in gene cloning is to allow the host cell to multiply, forming a clone having millions of identical cells.
By this process a piece of genetic information can be transferred into a cell where it would never occur naturally. In a very limited sense a new organism is created. Simply cloning a piece of DNA will not do much good. The information in DNA must be converted into a useful product. Let us take an example. Insulin is a controlling type of protein. The insulin gene is a region in the DNA that contains information for producing insulin. Some diabetic patients fail to produce sufficient quantities of insulin and thus are unable to properly control their sugar metabolism; consequently, these diabetic patients must take daily injections of insulin. Before the development of genetic engineering, insulin could be obtained only by an expensive process of extracting the protein from hog (pig) pancreas. Now, through gene cloning techniques, human insulin genes have been placed in bacteria. Hog insulin is not advocated for the following reasons:
	(i) Some people are allergic to it, (ii) it is very expensive, and (iii) many animals have to be slaughtered. By genetic engineering insulin is made inside bacteria. Thus large quantities of insulin are now produced by bacteria.. It is much easier to obtain insulin from bacteria than from pancreatic tissue. Moreover, the engineered bacteria produce human insulin.

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