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| Sunday, 29 May 2005 |
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Junior Observer |  |
| News Business Features Editorial
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To clone or not ...
Have you heard about cloning? Though you may not know what cloning means, you may have at least heard the word or heard about Dolly, the first cloned mammal. In simple words, cloning is the process of making a genetically identical organism using technology. For example, scientists can make another person identical to you in a laboratory (yes, just like you have seen in the movies) using advance scientific methods. Nature has been cloning organisms for billions of years. For example, when a potato plant sends out a runner (a form of modified stem), a new plant grows where the runner takes root. This new plant is a clone. Similar cloning occurs in grass and onions. People have been cloning plants in one way or another for thousands of years. For example, when you take a leaf cutting from a plant and grow it into a new plant (vegetative propagation), you are cloning the original plant because the new plant has the same genetic make-up as the other plant. Vegetative reproduction works because the end of the cutting forms a mass of non-specialised cells called a 'callus'. With luck, the callus will grow, divide and form various specialised cells (roots, stems), eventually forming a new plant. More recently, scientists have been able to clone plants by taking pieces of specialised roots, breaking them up into root cells and growing the root cells in a nutrient-rich culture. In this culture, the specialised cells become unspecialised (de-differentiated) into calluses. The calluses can then be stimulated with the appropriate plant hormones to grow into new plants that are identical to the original plant from which the root pieces were taken. This procedure, called tissue culture propagation, has been widely used by horticulturists to grow prized orchids and other rare flowers. Plants are not the only organisms that can be cloned naturally. The unfertilised eggs of some animals (small invertebrates, worms, some species of fish, lizards and frogs) can develop into full-grown adults under certain environmental conditions - usually a chemical stimulus of some kind. This process is called parthenogenesis, and the offspring are clones of the females that laid the eggs.
Another example of natural cloning is identical twins. Although they are genetically different from their parents, identical twins are naturally occurring clones of each other. Scientists have experimented with animal cloning, but have never been able to stimulate a specialised (differentiated) cell to produce a new organism directly. Instead, they rely on transplanting the genetic information from a specialised cell into an unfertilised egg cell whose genetic information has been destroyed or physically removed. In 1997, cloning became a popular topic when Ian Wilmut and his colleagues at the Roslin Institute in Edinburgh, Scotland, successfully cloned a sheep named Dolly. Dolly was the first cloned mammal. Since Dolly, several university laboratories and companies have used various modifications of the nuclear transfer technique to produce cloned mammals, including cows, pigs, monkeys, and mice. Why clone? The main reason to clone plants or animals is to mass produce organisms with desired qualities, such as a prize-winning orchid or a genetically engineered animal - for instance, sheep have been engineered to produce human insulin. If you had to rely on breeding alone to mass-produce these animals, then you would run the risk of breeding out the desired traits because normal sexual reproduction reshuffles the genetic composition. Other reasons for cloning might include replacing lost or deceased family pets and repopulating endangered or even extinct species. Whatever the reasons may be, new cloning technologies have sparked many ethical debates among scientists, politicians and the public about the use and morality of cloning plants, animals and possibly, humans. Several governments have considered or enacted legislation to slow down, limit or ban cloning experiments outright. It is clear that cloning will be a part of our lives in the future, but the course of this technology has yet to be determined. Source :Internet ############ Poisonous chemical compounds Have you heard the word 'dioxins' before? To those of you studying Chemistry, as an area of science, in school, this word may not be totally unfamiliar. Dioxins are a class of compounds, which means there could be hundreds of different chemicals categorised as dioxins. However, all have a similar basic chemical structure and because of this, similar biological effects. Another similarity is that all contain chlorine atoms. Some dioxins like tetra-chloro dibenzo dioxin (TCDD) are poisonous. But not all of them have the same effect on the body. TCDD, for instance, interferes with body cells, inflicting different effects on the different organs of the body. they may adversely affect the liver and reproductive system. Short-term effects of TCDD include pain, tiredness and acne-like rashes while long-term effects could include cancer and diabetes. So, how are these compounds released into the environment? They may be released through combustion, which is the burning of wastes, fossil fuels and plastic, industrial processes such as chlorine bleaching of paper and pulp, cigarette smoke and through certain herbicides. A natural forest fire can also release dioxins into the air around us. They are so common in the modern environment that all of us may have some dioxin in our blood. One reason why they are so widespread is because they are not easy to decompose. They spread quickly, accumulate in the fat reservoirs of living beings and concentrate up the food chain. All of them are not poisonous however and the effects of the poisonous varieties also depend on factors such as the state of health of the affected person and the time and duration of exposure to the compound. |
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