one page report on the Genetic engineering article
one page report on the attached genetic engineering article, minimum 300 words
3/15/2021 Genetic engineering — Britannica Online Encyclopedia
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TABLE OF CONTENTS
Introduction
Historical developments
Process and techniques
Applications
Controversy
genetic engineering
A genetically engineered salmon (top)
and a natural salmon of the same age
(bottom). The ability to engineer and
precisely edit the genomes of animals,
while potentially beneficial, has raised
ethical questions.
Paul Darrow—The New York
Times/Redux
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.
Historical
developments
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
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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 has advanced the understanding of many theoretical and practical aspects
of gene function and organization. Through recombinant DNA techniques, bacteria have been
created that are capable of synthesizing human insulin, human growth hormone, alpha
interferon, a hepatitis B vaccine, and other medically useful substances. Plants may be
genetically adjusted to enable them to fix nitrogen, and genetic diseases can possibly be
corrected by replacing dysfunctional genes with normally functioning genes. Nevertheless,
special concern has been focused on such achievements for fear that they might result in the
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genetically engineered corn
(maize)
Genetically engineered corn (maize).
© S74/Shutterstock.com
introduction of unfavourable and possibly dangerous traits into microorganisms that were
previously free of them—e.g., resistance to antibiotics, production of toxins, or a tendency to
cause disease. Likewise, the application of gene editing in humans has raised ethical concerns,
particularly regarding its potential use to alter traits such as intelligence and beauty.
Controversy
In 1980 the “new” microorganisms created by
recombinant DNA research were deemed patentable, and
in 1986 the U.S. Department of Agriculture approved the
sale of the first living genetically altered organism—a
virus, used as a pseudorabies vaccine, from which a
single gene had been cut. Since then several hundred
patents have been awarded for genetically altered
bacteria and plants. Patents on genetically engineered
and genetically modified organisms, particularly crops and other foods, however, were a
contentious issue, and they remained so into the first part of the 21st century.
The Editors of Encyclopaedia Britannica
This article was most recently revised and updated by Kara Rogers, Senior Editor.
Citation Information
Article Title: Genetic engineering
Website Name: Encyclopaedia Britannica
Publisher: Encyclopaedia Britannica, Inc.
Date Published: 22 May 2020
URL: https://www.britannica.com/science/genetic-engineering
Access Date: March 15, 2021
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