GENETIC ENGINEERING (Part 1 of 2)   Leave a comment

DEFINITION: the branch of biology dealing with the splicing, and recombining, of specific genetic units from the DNA of living organisms: it is used to modify the existing genetic codes to produce new, or improved, species, valuable biochemicals.

1865: The birth of genetics. It was unfortunate for the biological sciences that Gregor Mendel was an obscure Austrian monk. His pioneering work in the field of genetics was being done at the time that Charles Darwin’s publications on evolution were beginning to create worldwide controversy, but Mendel’s work would remain unknown for years.

Mendel became an Augustinian monk in 1843, but his abilities in mathematics and the sciences were evident. His experiments on the principles of heredity were begun in about 1856 in what is now Czechoslovakia. By crossing various strains of peas with one another, Mendel found that traits were passed on from generation to generation in what he called “discrete hereditary elements” in sex cells, or gametes.

Mendel reported the results of his experiments to a local society for the study of natural science in 1865 and published his findings in the society’s journal. They were as good as buried there for the next 35 years. Although the journal found its way to libraries in Europe and North America, few paid any attention to his writings. When other botanists obtained results similar to Mendel’s, they began searching through earlier writings on the subject. Only then was Mendel’s 1865 research revealed. His “discrete hereditary elements” are now called genes, and the new science once called Mendelism is known as genetics.

1953: Discovery of DNA structure. The full name of DNA is deoxyribonucleic acid. It carries the codes of genetic information that transmit inherited characteristics to successive generations of living things.

DNA was discovered in 1869 by Friedrich Miescher. In 1943 its role in inheritance was demonstrated. In 1953 its structure was determined by an American biochemist, James D. Watson, and an English physicist, Francis H.C. Crick. Watson and Crick showed the structure to be two strands of a phosphoryl-deoxyribose polymer arranged as a double helix. Watson and Crick were awarded the Nobel prize in physiology or medicine in 1962.

1973: Biotechnology. Two American biochemists, Stanley H. Cohen and Herbert W. Boyer, inaugurated the science of genetic engineering and its associated field of biotechnology in 1973. They showed that it was possible to break down DNA into fragments and combine them into new genes, which could in turn be placed in living cells. There they would reproduce each time a cell divided into two parts.

Genetic engineering makes it possible to modify existing organisms or create organisms that already exist in the human body but that are difficult to isolate. For example, one early product was a genetically engineered form of insulin, used in the treatment of diabetes. Other genetically engineered products include interferons, which are used in the treatment of viral infections and showed promise in the treatment of various forms of cancer. Scientists hope that genetically engineered products will someday prevent or cure such genetic disorders as muscular dystrophy and cystic fibrosis.

Genetic engineering also opens the possibility of creating entirely new organisms. In 1980 the United States Supreme Court ruled that newly developed organisms could be patented, thus giving ownership rights to the companies that made them.

Chromosome, microscopic, threadlike part of the cell that carries hereditary information in the form of genes; among simple organisms, such as bacteria and algae, chromosomes consist entirely of DNA and are not enclosed within a membrane; among all other organisms chromosomes are contained in a membrane-bound cell nucleus and consist of both DNA and RNA; arrangement of components in the DNA molecules determines the genetic information; every species has a characteristic number of chromosomes, called the chromosome number; in species that reproduce asexually the chromosome number is the same in all the cells of the organism; among sexually reproducing organisms, each cell except the sex cell contains a pair of each chromosome.

Each human cell holds a vast storehouse of genetic information in some 100,000 genes, which code for individual biochemical functions, strung out along 46 chromosomes. Collectively, this storehouse forms the human genome. The techniques of genetic engineering allow scientists to identify specific genes, to remove any one of those genes from an organism’s chromosome, to clone or make a large number of identical copies of that gene, to analyse a copy in detail, to modify it, and to reinsert it into the genetic material of the organism from which it was derived or into the genetic material of a similar or very different organism.

The development of genetic engineering has had a great influence on science and business and has begun to radically alter medicine and agriculture. One of the first steps in shedding new light on human evolution and in controlling or altogether eliminating many diseases was taken in the early 1990s. Scientists mapped, or took apart, the smallest human chromosomes: the Y chromosome and chromosome 21. Breaking these chromosomes into small pieces allowed researchers to reproduce these segments in large quantities. Researchers believe that this, in turn, will lay the groundwork for mapping and eventually controlling all genes, including those that may be responsible for certain diseases.

Recombinant DNA, genetically engineered DNA prepared in vitro by cutting up DNA molecules and splicing together specific DNA fragments; usually uses DNA from more than one species of organism.

Smith, Hamilton O. (born 1931), U.S. microbiologist, born in New York City; with U.S. Public Health Service 1962-67; at School of Medicine of Johns Hopkins University from 1967, professor from 1973; received 1978 Nobel prize for research on effect of restriction enzymes on DNA molecules.

Nathans, Daniel (born 1928), U.S. microbiologist, born in Wilmington, Del.; professor school of medicine of Johns Hopkins University from 1967, director microbiology department from 1972; received 1978 Nobel prize for research on effect of restriction enzymes on DNA molecules.

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Posted 2012/02/25 by Stelios in Education

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