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History of genetics


Gregor Mendel, the "father of genetics" The first recorded scientific study of how traits pass from one generation to the next was done by Mendel. While teaching, Mendel took over a garden plot at his monastery. In 1856, he began experimenting with garden peas. His observations of his fathers orchard made him think that it was possible to predict the kinds of flowers and fruit a plant would produce. After eight years of work on inheritance in pea plants, Mendel presented a paper detailing the results of his research to the Natural Science Society in Brunn, Austria. In the centuries before—and for several decades after—Mendel's work, a wide variety of theories of heredity proliferated. 1900 marked the "rediscovery of Mendel" by Hugo de Vries, Carl Correns and Erich von Tschermak, and by 1915 the basic principles of Mendelian genetics had been applied to a wide variety of organisms—most notably the fruit fly Drosophila melanogaster. Led by Thomas Hunt Morgan and his fellow "drosophilists", geneticists developed the Mendelian-chromosome theory of heredity, which was widely accepted by 1925. Alongside experimental work, mathematicians developed the statistical framework of population genetics, bring genetical explanations into the study of evolution. With the basic patterns of genetic inheritance established, many biologists turned to investigations of the physical nature of the gene. In the 1940s and early 1950s, experiments pointed to DNA as the portion of chromosomes (and perhaps other nucleoproteins) that held genes. A focus on new model organisms such as viruses and bacteria, along with the discovery of the double helical structure of DNA in 1953, marked the transition to the era of molecular genetics. In the following years, chemists developed techniques for sequencing both nucleic acids and proteins, while others worked out the relationship between the two forms of biological molecules: the genetic code. The regulation of gene expression became a central problem in the 1960s; by the 1970s gene expression could be controlled and manipulated through genetic engineering. In the last decades of the 20th century, many biologists focused on large-scale genetics projects, sequencing entire genomes.

Genetic Engineering
For thousands of years genetics has made an impact on agriculture. When farmers, ranchers, and herders employ selective breeding to increase their yield, they are using a kind of genetic engineering. They control the reproduction of their plants and animals so that each new generation has as many beneficial genes as possible. With such a history, then, it is no wonder that now, at the dawn of the twenty-first century, agriculture is one of the industries leading the way in cutting-edge gene manipulation techniques. Transgenic Animals Transgenic animals are animals that have had foreign genes implanted into their DNA structure. These genes often help the animal fight diseases, grow stronger, or withstand harsh environments. An antifreeze producing gene, for example, taken from cold water flounder has been inserted into certain kinds of salmon so that they can be raised in colder climates. To make an animal transgenic, foreign genes must be inserted into a freshly fertilized egg before it begins to develop. The first step is to identify the desired gene in the donor cells. Once the target is found, restriction enzymes are used to cut the gene out of its DNA chain. Next, the gene is clipped into the DNA molecule of a bacterium, which will act as the carrier of the trait to the animal. The bacteria carriers are then allowed to grow into a colony, and are radioactively tagged to ensure that they have the desired gene. Once the carrier is ready, it is used to transplant the gene into a host embryo. This embryo is then either duplicated or immediately inserted into a surrogate mother so that it may develop. Plants The process involved in genetically engineering a plant is similar to that for an animal. The target gene must be found, cut, and transplanted into a carrier organism which will implant it in the host. The benefits of manipulating plants in this manner are varied. Soybeans have been altered to increase their amino acid content (making them a healthier food source). Photosynthesis can be made more efficient in some green plants. Fruits can be given a strong resistance to bruising. A crop's defenses against disease and pests can be increased.

The Human Genome
There are forty-six chromosomes in the human body- about three billion base pairs worth of DNA. These extremely long molecules make up what is known as the human genome - the genetic code for perhaps as many as 100,000 complex genes. To make a map of this information, in other words to discern the exact location of every gene and find the base-pair sequences that creates it, would be a great scientific feat. Simply considering its potential impact on the field of medicine the effects of having such a map could be revolutionary. People could be tested for certain gene related diseases early enough to make necessary lifestyle changes or perhaps, when the technology becomes sophisticated enough, receive some sort of treatment or cure. The creation of such a map is an incredible undertaking, though, with an estimated price tag of billions of dollars and countless man-hours. The benefits outweigh the costs, however, and so scientists around the world are racing to help map the human genome. No project this large can be without controversy, and this is definitely no exception. Many feel that our money could be better spent elsewhere concentrating on treatment for specific diseases. Others, though, believe that the human genome project is the best possible expenditure of research dollars.

Cloning
Cloning is the process of artificially reproducing a gene, set of genes, or a whole organism. One of the most common uses of cloning is to create many identical copies of a certain gene. To accomplish this, the gene is isolated and then inserted into a bacterium. The bacterium is then allowed to reproduce, copying the inserted gene with it. This method is currently being used in the human genome project to make copies of human genes to study. Cloning is also used in agriculture to produce identical reproductions of a crop. A tissue sample can be cut from a parent plant and then exposed to a mixture of nutrients and specially manipulated hormones that cause it to grow roots. At that point the clone can be transferred into soil and grown normally. Thousands of offspring can be created from a single plant using this method by simply dividing the tissue sample before it is able to take root. Using these ideas scientists have been able to create artificial "seeds" from cells that would otherwise never be able to reproduce. The benefits to such crops are many: strong plants can be isolated for reproduction without wasting resources on plants with poor yields, genetically identical plants mature at the same rate simplifying the harvest season, and yields are generally more dependable. The drawbacks are the costs and the reduction of genetic diversity. A disease that threatens one plant will also threaten all of its clones. Recently geneticists have taken cloning a step further and have begun to successfully work with animals. In 1997 Scottish scientists announced that they had made the first clone of a mammal by taking the genetic information from an adult sheep and inserting it into an egg, which was then allowed to mature in a surrogate mother. The resulting offspring was proven to have genes that were identical to its parent. This startling breakthrough has many implications, especially when one considers that a similar process would probably work with humans.