Read the following extract and find out what cloning is and how far the experimental techniques have developed.

Cloning

Cloning, creating a copy of living matter, such as a cell or organism. The copies produced through cloning have identical genetic makeup and are known as clones. Many organisms in nature reproduce by cloning. Scientists use cloning techniques in the laboratory to create copies of cells or organisms with valuable traits. Their work aims to find practical applications for cloning that will produce advances in medicine, biological research, and industry.

I overview

Genetic Engineering enables scientists to produce clones of cells or organisms that contain the same genes. Scientists are getting better at all kinds of cloning – from individual cells to entire organisms. The results are as follows: 1) Certain primitive cells found in the brain, blood and elsewhere remain undeveloped enough even in adults that they can grow into a limited number of cell types. The cells might be coaxed to become a wider variety of tissues. 2) Researchers have successfully isolated stem cells from 5-day-old human embryos that were created during in-vitro fertilization and would otherwise have been destroyed. Unlike adult stem cells, embryonic stem cells can develop into any of more than 200 tissues in the body, fron insulin-producing cells that may one day treat diabetes to heart cells that may repair cardiac muscle. 3) Since adult stem cells are rare, scientists may be able to use tissue that is more easily available, such as the skin. In one method, researchers replace the genetic material from a donor egg with the nucleus of a skin cell; the new hybrid begins to grow like an embryo from which stem cells can be isolated. These in turn could produce transplants that are immunologically identical to the original host and therefore would not be rejected.

Farmers started cloning plants thousands of years ago in simple ways, such as taking a cutting of a plant and letting it root to make another plant. Early farmers also devised breeding techniques to reproduce plants with such characteristics as faster growth, larger seeds, or sweeter fruits. They combined these breeding techniques with cloning to produce many plants with desired traits. These early forms of cloning and breeding were slow and sometimes unpredictable. By the late 20th century scientists developed genetic engineering, in which they manipulate deoxyribonucleic acid (DNA), the genetic material of living things, to more precisely modify a plant’s genes. Scientists combine genetic engineering with cloning to quickly and inexpensively produce thousands of plants with a desired characteristic.

Cloning techniques can also be applied to animals. Scientists generate genetically modified animals with new traits, such as the ability to resist disease, and they use cloning techniques to reproduce these genetically modified animals. In the near future scientists hope to bolster populations of endangered species by cloning members from existing populations. Someday scientists may even resurrect extinct species by cloning cells from preserved specimens.

Industry also utilizes cloning technology. For example, some bacteria eat toxic substances, such as gasoline or industrial chemicals, that are common pollutants. These bacteria can be cloned to make legions of bacteria with the ability to clean up environmental contamination (see Bioremediation). Likewise, cloned animals can be used to make a variety of ingredients, such as proteins, that are used in many commercial products.

Perhaps most important from a human perspective, cloning promises great advances in medicine. Scientists have already inserted fragments of DNA containing the human gene for a blood-clotting protein into cells of a sheep. Through cloning techniques, scientists have generated new sheep whose milk contains the protein, which is needed by people with the blood-clotting disorder known as hemophilia. In the near future, researchers hope to use cloning to develop animals with human diseases and use these cloned animals to test the safety and effectiveness of new treatments devised for humans. Biomedical scientists hope to take cells from an ill patient, genetically modify them, and clone the modified cells to grow exactly the cells that the patient needs to regain health. Some scientists even imagine a day when cloning could be part of a process that grows entire organs for transplants.