genetic engineering

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Genetic Engineering

I . Introduction

During the nineteenth century , scientists showed that microorganisms were responsible for many useful functions , including the long-practiced production of bread , beer , wine , and cheese . As the science of microbiology developed , microbiologists learned how to isolate and grow microorganisms in pure culture . Once they had obtained pure strains they could select the ones that were more efficient than others in brewing beer , for example - this was a logical extension of the reasoning long used in selecting desirable breeds of animals

or strains of plants . Much more recently , scientists working with antibiotic-producing microbes discovered that they could create new strains by exposing the microbes to mutagenic radiation or chemicals Some of these variant strains produced more , or better , antibiotics This mutational approach was responsible for many advances in the industrial production of antibiotics following World War II (Old Primrose , 2001

During this period , scientists discovered recombination of DNA in microbes . Recombination occurs naturally in microorganisms , generally between the DNAs of closely related strains . In bacteria , the DNA of a donor strain may be brought into contact with the DNA of a donor strain may be a beneficial form of genetic change than are mutations , most of which are harmful to the bacterium and are not useful commercially

This intent to (1 ) defines recombinant DNA , cDNA , genetic engineering , vector , and protoplasts (2 ) describe restriction enzymes and outline how they are used to make recombinant DNA and (3 ) describe how a gene library is made and outline genetic engineering using transformation

II . Background

A . The Advent of Recombinant-DNA Technology

During the 1970s and 1980s , the practical application of microorganisms expanded almost beyond imagination with the development of new artificial techniques for making recombinant DNA . Although natural recombination makes it possible for closely related organisms to exchange genes , the new techniques make it possible to transfer genes between completely unrelated species . So very powerful are these techniques that the term recombinant DNA is now widely understood to refer DNA that has been artificially manipulated to combine genes from two different sources . A gene from vertebrae animal , such as human , can be inserted into the DNA of a bacterium , or a gene from a virus into yeast . In many cases , the recipient can then be made to express the gene , which may code for a commercially useful product . For example bacteria with genes for human insulin are now being used to produce insulin for treating diabetes (Old Primrose , 2001 . Also , a vaccine for hepatitis B is being made by yeast carrying a gene for part of the hepatitis virus the yeast produces a viral protein . Scientists hope that such a protein may prove to be an effective vaccine , eliminating the need to use whole viruses as in conventional vaccines . In a lighter vein , scientists working to refine recombinant-DNA procedures in plants have succeeded in transferring a firefly gene to a tobacco plant and getting into function

The new recombinant-DNA techniques can also be used to make thousands...