Cloning occurs when you copy a living creature. Two clones have the same genes, small structures with information in them that tells them what the body of a living thing should look like and how it should behave. You get the genes from your parents.
Many people think that cloning is only done by scientists in laboratories, but, in fact, cloning also occurs in nature.
Animals have billions of cells. The nucleus of such a cell has genetic information called DNA. All the nuclei of an animal have the same information. But each cell only uses a part of this information in order to work properly. The other part of the DNA is not active. But because a single cell holds all the DNA of an animal, scientists can make physical copies of an animal from only one cell.
They transfer the nucleus of an animal’s cell into an egg cell of another animal. This egg cell has the same genetic information as that of the donor animal. The cell then grows into an embryo. Scientists must then activate the DNA that was not active in the parent cell. Otherwise a full organism would not develop.
Clones do not behave in an identical way – this is because they live in different environments. Researchers have found out that identical twins that carry the same DNA are different because they grow up differently.
History of cloning
Cloning animals started way back in the 1950s when the first frogs were reproduced. In 1996 British scientists cloned the first mammal, a sheep called Dolly. Since then the cloning of mice, cattle, cats and other mammals has been successful.
Pros and cons of cloning
The cloning of certain animals may bring advantages to humans. The cloning of cattle or sheep can produce animals whose meat quality is better or which are more resistant towards illnesses.
Scientists, however, cannot yet create perfect clones. Many of them do not survive the cloning process and die before they are born.
In the past human embryos have been cloned in order to get stem cells. These are cells that can develop into many different kinds of other cells. Doctors are able to use stem cells to replace parts of the body that are ill, like skin or other organs. Although this could be a major breakthrough in medicine many people fear that cloning embryos is murder and must therefore be forbidden. Many countries have put bans on cloning or other experiments that produce cloned human embryos.
Some scientists still believe that it may be possible to clone a human being from the cells of one adult. For a long time this has been thought of as science fiction.
Many problems arise when it comes to cloning human beings. What should be the ideal characteristics of reproduced humans: should they be highly intelligent, strong or creative. Who are the people to decide these questions? Critics of cloning say that creatures should be born in a natural way. Nobody has the right to play God.
Clones occur naturally in many cases, for example, when a mother gives birth to two identical twins. They come from the same fertilized eggs and are therefore have identical genes. Bacteria and animals with only one cell can also reproduce themselves in a natural way. Plants can also produce clones. Farmers use breeding techniques to produce certain types of plants.
Reasons for cloning
Cloning is often performed for medical reasons. Experiments are carried out on animals that carry a disease which causes mutations in their genes. Farm animals are cloned to produce drugs and other substances that are useful in medicine. Cloning is a way to produce large numbers of genetically engineered animals.
In therapeutic cloning stem cells are reproduced in order to create new organs and tissue. New, healthy tissue can help a person get a new heart or a new liver to replace his ill one. Such a method could also create stem cells that you could use for patients who suffer Alzheimer’s or Parkinson’s disease.
Downloadable PDF Text- and Worksheets
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- activate = to make something work
- advantage = the good side of something
- although = while
- Alzheimer’s disease = a disease that affects the brain, especially of older people; it makes it difficult to walk , move or remember things
- bacteria = small living things, some of which can cause an illness
- ban = to forbid something
- behave = act
- billion = a thousand million
- birth = to produce a baby from your body
- breakthrough = step forward
- breeding technique = the method of keeping animals and plants together in order to produce living things that have the same or different features
- cattle = cows kept on farms for their milk or meat
- certain = special
- characteristic = feature, quality
- creature = a living thing
- critic = a person who is against an idea
- develop = grow
- disease = illness
- donor = giver
- drugs = medicine
- embryo = an animal or plant that has not yet been born and has just begun to grow
- environment = the world around us
- fertilize = to make a new plant or new life grow
- forbid = not allow
- genetic = about a gene
- genetically engineered = to change the structure of an animal or plant so that they are not affected by diseases or harmful insects
- identical = the same
- illness = disease
- laboratory = place, where scientists carry out experiments
- major = big
- mammal = animal that drinks milk from its mother’s body when it is young
- mutation = a change in the genes of an animal, plant or person that makes it different from others
- nucleus = center
- occur = happen
- otherwise = or else, if not
- Parkinson’s disease = a serious illness in which your muscles become very weak and your arms and legs become shaky
- patient = a person who is ill
- perform = do
- physical = about the body
- properly = correctly
- pros and cons = good and bad sides
- replace = exchange, put in something’s place
- reproduce = copy, clone
- researcher = a person who studies a topic and tries to find out more about it
- resistant = to stand against
- science fiction = stories about events in the future that are about things we have not yet developed, like travelling in time etc..
- scientist = a person who is trained in science and works in a laboratory
- stem cell = a special type of cell in the body that can divide in order to form other types of cells that have a special use
- structure = building block
- substances = material
- successful = here: to work in the right way
- suffer = to feel pain
- survive = to live on after a dangerous situation
- tissue = the material that forms animal or plant cells
- transfer = move
- twin = one of two children born at the same time to the same mother
- useful = helpful
- yet = up to now