Contents in this Web site >> DNA and Genetic Engineering concepts,  DNA information, DNA News, Related topics in French, Related topics in Spanish, Genetic Engineering (Ethics of science and the bioethics of genetic engineering, The latest on the science of the Human Genome Project, Governmental and International Control of Genetic Engineering, Human applications of genetic engineering including gene therapy and germline, Cloning, Genetic engineering in food production and agriculture, Educational resources, Worldwide news on genetic engineering developments, Worldwide news on genetic engineering developments, Campaigns and other non-governmental organisations related to genetic engineering, Sites dealing specifically with eugenics issues, Sites of transnational corporations engaged in genetic engineering and its applications, Organisations supporting the plant genetic engineering industry, World's first comprehensive governmental investigation into all aspects of genetic engineering...)

SCIENCE
DNA - GENETIC ENGINEERING
by Artur Coral, Jacques Lemoine and Yuko Hiroko

This model has the same atomic positions and balls colored by element, but now the sticks convey other information: the backbones are red and blue, and the bases are purple (Adenine), green (Thymine), yellow (Guanine), and cyan (Cytosine).

MAPPING OF HUMAN GENETIC CODE - GENETIC MAP HAILED AS SCIENTIFIC REVOLUTION The 10-year Human Genome Project is being called a scientific milestone and ultimately could let doctors correct genetic flaws before birth. MANHATTAN, NEW YORK, USA. June 26, 2000. - Two teams of scientists have completed a rough draft of the human genetic code -- nature's instructions for making and maintaining human beings -- in a breakthrough likened to a medical version of putting man on the moon. Scientists confirmed Monday that a working draft of the human genetic code has been completed, marking a scientific milestone that will transform the understanding, treatment and prevention of disease. By Artur Coral, Jacques Lemoine and Yuko Hiroko NEW YORK . PARIS . TOKYO

James D. Watson, Ph.D STAFF ARTUR CORAL: Doctor in Bio-Medical Sciences, Paris, France. JACQUES LEMOINE: Bio-Medical Engineer, New York, USA. YUKO HIROKO: Medical Doctor and Nuclear Medicine Specialist, Tokyo, Japan.

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CONCEPTS / NOTES

• The word has conjured fear and dread in the 13 million Americans diagnosed with it in the last decade: cancer.
• Cancer can develop at any time in any tissue or organ. It is uncontrolled cell growth with the ability to spread to other areas of the body.
• About 550,000 Americans are expected to die of cancer this year, more than 1,500 per day. Some 1.2 million new cases will be discovered.
• There is absolutely no question that this is going to be a defining moment in both disease and health in general and in particular cancer.
• Cancer is the most complex genetic disorder that we face. Understanding the enemy, understanding the genetic underpinnings of a cancer cell, is the first step in developing rational therapeutic strategies.
• "This is going to change the way all of medicine is practiced and that, of course, relates naturally to cancer, and particularly so because cancer is a disease of the genes,'' ``Will we ever get to a stage like polio or smallpox where we can totally eradicate cancer from the face of the Earth? In a way, we are entering the era of genetic and molecular medicine.''
• ``There's also the possibility that if we understand how normal cells become cancer cells, we can use medications to prevent that transformation.''
• The only real commercial application of genetics in cancer is identification of the BRCA genes known to be involved in the development of hereditary breast tumors.
• ``I think that what we are all excited about is the potential to use the new genetic information in a variety of ways for better early detection of cancer, for better assessing the prognosis of patients, for improving the selection of therapy.''
• It was announced this week was simply the location of genes on the various human chromosomes, not their function or how they interact with each other. Much work lies ahead.
• ``In a cancer cell we don't know how many changes there are, there may be thousands,'' he said. ``How you dissect out and deal with all those changes'' is critical.
• Researchers 15 or 20 years ago could not have conceived where genomics would be today. Given this progress, he said, it is only a matter of time before the rest of the puzzle gets figured out.
• ``I think it's likely that the genes that are being identified here don't act individually, they probably act in concert with other genes. I would imagine within the next 10 years we're going to have a whole lot more information on that.''

The chemical DNA was first discovered in 1869, but its role in genetic inheritance was not demonstrated until 1943. In 1953, James Watson and Francis Crick determined that the structure of DNA is a double-helix polymer, a spiral consisting of two DNA strands wound around each other. Each strand is composed of a long chain of monomer nucleotides. The nucleotide of DNA consists of a deoxyribose sugar molecule to which is attached a phosphate group and one of four nitrogenous bases: two purines (adenine and guanine) and two pyrimidines (cytosine and thymine). The nucleotides are joined together by covalent bonds between the phosphate of one nucleotide and the sugar of the next, forming a phosphate-sugar backbone from which the nitrogenous bases protrude. One strand is held to another by hydrogen bonds between the bases; the sequencing of this bonding is specific--i.e., adenine bonds only with thymine, and cytosine only with guanine.

The configuration of the DNA molecule is highly stable, allowing it to act as a template for the replication of new DNA molecules, as well as for the production (transcription) of the related RNA (ribonucleic acid) molecule. A segment of DNA that codes for the cell's synthesis of a specific protein is called a gene.

DNA
NUCLEIC ACID found in the nuclei of CELLS. It is the principal constituent of GENES (linear segments of DNA) and CHROMOSOMES, the structures that transmit hereditary characteristics. The amount of DNA is constant for all typical cells of any given species of plant or animal, regardless of the size or function of that cell. Each DNA molecule is a long, two-stranded chain made up of subunits, called nucleotides, containing a sugar (deoxyribose), a phosphate group, and one of four nitrogenous bases: adenine (A), guanine (G), thymine (T), and cytosine (C). In 1953 J.D. WATSON and F.H. CRICK proposed that the strands, connected by hydrogen bonds between the bases, were coiled in a double helix. Adenine bonds only with thymine (A-T or T-A) and guanine only with cytosine (G-C or C-G). The complementarity of this bonding insures that DNA can be replicated, i.e., that identical copies can be made in order to transmit genetic information to the next generation. See also HUMAN GENOME PROJECT.

GENETIC ENGINEERING
Steps involved in the engineering of a recombinant DNA molecule.
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 meant any of a wide range of techniques 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), sperm banks, cloning, and gene manipulation. But the term now denotes the narrower field 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. Gene cloning is used to produce new genetic combinations that are of value to science, medicine, agriculture, or industry.

DNA is the carrier of genetic information; it achieves its effects by directing the synthesis of proteins. 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.

CLONE / CLONING

also spelled CLON, population of genetically identical cells or organisms that are derived originally from a single original cell or organism by asexual methods. Cloning is fundamental to most living things, since the body cells of plants and animals are clones ultimately derived from the mitosis of a single fertilized egg. More narrowly, a clone can be defined as an individual organism that was grown from a single body cell of its parent and that is genetically identical to it.

Plants that are able to propagate by asexual means produce genetically identical plants that are clones. Cloning has been commonplace in horticulture since ancient times; many varieties of plants are cloned simply by obtaining cuttings of their leaves, stems, or roots and replanting them. A vast array of fruit and nut tree varieties and innumerable ornamental plants represent clones.

The body cells of adult animals and humans can be routinely cloned in the laboratory. Adults cells of various tissues, such as muscle cells, that are removed from the donor animal and maintained on a culture medium while receiving nutrients manage not only to survive but to go on dividing, producing colonies of identical descendants. By the 1950s scientists were able to clone frogs, producing identical individuals that carry the genetic characteristics of only a single parent. The technique used in the cloning of frogs consists of transplanting frog DNA, contained in the nucleus of a body cell, into an egg cell whose own genetic material has been removed. The fused cells then begin to grow and divide, just like a normal fertilized egg, to form an embryo.

Mice were first successfully cloned in the 1980s, using a procedure in which the nucleus from a body cell of a mouse embryo is removed from the uterus of a pregnant mouse and transplanted into a recently fertilized egg (from another mouse) whose genetic contents have been evacuated. The cell is cultured artificially until it divides and becomes an embryo. The embryo, which is composed entirely of cells derived from the single implanted nucleus, is artificially implanted into the uterus of another mouse that brings it to term.

Cloning a new animal from the cells of an adult (as opposed to those of an embryo) is considerably more difficult, however. Almost all of an animal's cells contain the genetic information needed to reproduce a copy of the organism. But as cells differentiate into the various tissues and organs of a developing animal, they express only that genetic information needed to reproduce their own cell type. This tended to restrict animal cloning to the use of embryonic cells, which have not yet differentiated into blood, skin, bone, or other specialized cells, and which can more easily be induced to grow into an entire organism.

The first success in cloning an adult mammal was achieved by a team of British researchers led by Ian Wilmut at the Roslin Institute in Edinburgh, Scot., in 1996. After having already produced clones from sheep embryos, they were able to produce a lamb using DNA from an adult sheep. In their procedure, the nucleus of a cell from the mammary gland of an adult sheep was implanted in another sheep's unfertilized egg whose nucleus had been removed. The key to the new procedure is to synchronize the cell cycle--i.e., the ordered sequence of events that occur in a cell in preparation for division--of the mammary cell with that of the egg. To achieve this, before implantation the mammary cell is deprived of nutrients; this stops its cell cycle, thus preventing it from dividing. The nucleus is then implanted into the recipient egg and fused to it, and an electrical current is applied to simulate the burst of energy that occurs during fertilization. The egg begins dividing normally and becomes an embryo, which is implanted into another ewe. The lamb that is born is a clone of the donor of the original mammary cell.

The practical applications of cloning are economically promising but philosophically unsettling. Animal breeders would welcome the chance to clone top-quality livestock. Genetically engineered animals could be cloned in large numbers to increase the production of drugs or human proteins that are useful in fighting disease. Clones are also highly useful in biological research because of their genetic uniformity.

The cloning of human beings is a subject fraught with ethical and moral controversy. If cloning can ensure the infinite replication of specific genetic traits, a judgment would need to be made as to which traits are desirable and therefore worthy of perpetuation. The persons empowered to exercise such judgment would be in a position to change the course of human development.

The use of recombinant DNA technology to manipulate and change genes is sometimes called gene cloning.

 

DNA INFORMATION

• American Scientist: The Invention of the Genetic Code - on the work of Watson and Crick.
• Crick, Francis (1916- ) (7)
• DNA Molecule: Two Views - the double helix of the DNA is shown with details of how the bases, sugars, and phosphates connect to form the structure of the molecule.
• DNA Structure - graphic representation.
• DNA Structure Model Building - an exercise for students to use CPK models to build part of a DNA molecule.
• Few Words About DNA and Chromatin, A - well actually a lot of words, plus illustrations.
• Is Native DNA A Helix? - argues that DNA is not a helix in living systems.
• Molecular Structure of Nucleic Acids - the original paper by James Watson and Francis Crick which was published in the journal Nature in 1953.
• Reader's Guide to The Double Helix - commentary and explanation to accompany the book by James Watson.
• Structure of DNA - very simple illustration of the double helical structure.
• Watson, James (5)
• GENOMICS
• Mapping human DNA
• DNA from the begining
• DNA Research
• Everithing about DNA to Z
• DNA Graphics Created with PovChem
• Picture It Genetics - Links to interactive fruit fly lab, karyotype images, DNA visualizations, mitosis and meiosis, and evolution graphics.
• An Introduction to DNA Research
• Human Genome Sequencing Nearly Complete. Full coverage: Yahoo
• Computing Science.- The Invention of the Genetic Code
• DNA Molecule - Two Views
• A structure for Deoxyribose Nucleic Acid
• JAMES DEWEY WATSON - Biography
• Dr. James Watson - excerpt from an interview with the co-discoverer of the structure of DNA.
• Cold Spring Harbor Laboratory photo: Mason's of Cambridge - James D. Watson, Ph.D.
• Is Native DNA A Helix?
• GenLink
• Amorphous Computing
• Biochemical and DNA-Based Nanocomputers
• DNA Computers - a detailed description of how DNA based computers work and what they can do.
• DNA Computing and Informatics at Surfaces - research project aimed at the development and characterization of complex mixtures of DNA molecules attached to surfaces.
• Erik's Molecular Computation Page
• Everyone's Guide to DNA Computers - an excellent introduction to DNA computers.
• Publications on Molecular Computers
• Web Directory: Dave's Deoxyribonucleic Acid Page
• Wired 3.08: Gene Genie
• DNA 2
• DNA 2 Site - features images and character information.
• Vermilion's DNA 2 Page - includes character information and story summaries.