Ezen a héten egy kicsit nehezebb szövegeket fogunk olvasni a tudomány témakörében (középfokú nyelvvizsgán el?forduló szövegek nehézségi fokán). Ma a klónozással fogunk foglalkozni általánosságban, holnap pedig megismerkedünk a néhai Dolly-val, a birkával.
What is cloning? Cloning means making a living thing from another living thing such as a plant or animal. The process uses the genes of the first so they both have identical DNA.
Isn't it unnatural? Cloning isn't new. Nature's been doing it for billions of years with plants. Things like potatoes and grass send out shoots which can grow into a whole new plant. If you grow a plant form a cutting it's a type of cloning. And identical twins are naturally-occurring clones of each other even though they are genetically different from their parents.
So why is it in the news? In the last few decades scientists have been trying to clone animals. They transplant DNA (the gene pattern which makes living things unique) from the cell of one animal into the cell of another which has had its DNA taken out. Now scientists in America have announced that they have created a clone of a human embryo.
Does cloning work? In 1997 Dolly the sheep became the first ever cloned mammal. Scientists in Scotland used a new type of technique. When Dolly was born months later, it had taken 276 tries to get it right. Since Dolly cows, pigs, monkeys, rodents, cats, mules and horses have been cloned.
Why clone animals? Animals or plants with special qualities could be mass produced to help in the manufacture of important drugs. You could replace pets which have died or even repopulate endangered or even extinct species. Earlier this year, the first clone of an endangered animal was born: a baby bull gaur (a wild ox) called Noah. Although Noah died of an unrelated infection, the experiment showed it is possible to save endangered species through cloning.
Can people be cloned? There's a lot of controversy over this one. An announcement by an American company that it has created a human embryo clone is being viewed as both an incredible scientific achievement and a dangerous step. This is not the first time such a claim has been made. Opponents of cloning say cloning humans is very wrong because it goes against nature.
Why would we want to clone ourselves? It doesn't have to be a whole human being which is cloned. Scientists could copy our cells and fix genes that cause diseases. Our skin or hearts could be grown to help people who are ill. People who can't have babies might also be helped.
What is the problem with cloning? About 98% of cloning efforts fail. Usually a cloned embryo dies before birth but sometimes afterwards too. Most of the survivors have potentially fatal heart or lung problems or diseases like diabetes.
GLOSSARY FOR THIS UNIT
controversy cutting decade diabetes DNA effort embryo endangered extinct fatal genes genetically human identical incredible scientific achievement infection living thing lung mammal mass produce mule naturally-occurring opponents of cloning pattern process rodent shoot species survivor to announce to replace to repopulate to transplant unique unnatural unrelated
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