Biología, Botánica, Genética y Zoología

Clone # Clonación

Clone: an organism, or group of organisms, derived from another organism by an asexual (nonsexual) reproductive process. The word clone has been applied to cells as well as to organisms, so a group of cells stemming from a single cell is also called a clone. Usually the members of a clone are identical in their inherited characteristics—that is, in their genes —except for any differences caused by mutation. Identical twins, for example, who originate from the division of a single fertilized egg, are members of a clone; whereas non-identical twins, derived from two separate fertilized eggs, are not clones. Besides the organisms known as prokaryotes (the bacteria and cyan bacteria), a number of other simple organisms, such as most protozoans, many other algae, and some yeasts, also reproduce primarily by cloning, as do certain higher organisms like the dandelion or aspen tree.

Through recent advances in genetic engineering, scientists can isolate an individual gene (or group of genes) from one organism and grow it in another organism belonging to a different species. The species chosen as a recipient is usually one that can reproduce asexually, such as a bacterium or yeast. Thus it is able to produce a clone of organisms, or cells, that all contain the same foreign gene or genes. Because bacteria, yeasts, and other cultured cells multiply rapidly, these methods make possible the production of many copies of a particular gene. The copies can then be isolated and used for study (for example, to investigate the chemical nature and structure of the gene) or for medical and commercial purposes (for example, to make large quantities of a useful gene product such as insulin, interferon, and growth hormone). This technique is called cloning because it uses clones of organisms or cells. It has great economic and medical potential and is the subject of active research.

Identical-twin animals may be produced by cloning as well. An embryo in the early stage of development is removed from the uterus and split, and then each separate part is placed in a surrogate uterus. Mammals such as mice and sheep have been produced by this method, which is generally called embryo splitting.

Another development has been the discovery that a whole nucleus, containing an entire set of chromosomes, can be taken from a cell and injected into a fertilized egg whose own nucleus has been removed. The division of the egg brings about the division of the nucleus, and the descendant nuclei can, in turn, be injected into eggs. After several such transfers, the nuclei may be capable of directing the development of the eggs into complete new organisms genetically identical to the organism from which the original nucleus was taken. This cloning technique is in theory capable of producing large numbers of genetically identical individuals. Experiments using this technique have been successfully carried out with frogs and mice.

Progress in cloning higher mammals beyond an early embryonic stage presents a much more formidable challenge. Genes in cells at the earliest stages of embryonic life carry the encoded knowledge that enables cells to develop into any part of the body. But skeptics theorized that once cells form into specific body components, they thereafter lose the capability to reconstruct the entire organism from the genetic contents of the nucleus.

However, in July 1996, a team of Scottish scientists produced the first live birth of a healthy sheep cloned from an adult mammal. The team scraped skin cells from the udder of a donor sheep (sheep A) and these cells were temporarily starved of nutrients to halt cell development. An unfertilized egg was removed from a second sheep (sheep B) and its nucleus was removed to eliminate genetic characteristics of the donor egg. A skin cell from sheep A (containing a nucleus with genetic material) was fused with the unfertilized egg from sheep B. The egg, now with a full complement of genes, began dividing and was placed into the uterus of a surrogate mother (sheep C). The embryo developed normally and was delivered safely. Named Dolly, this healthy sheep was introduced to the world with much fanfare in February 1997.

While Dolly has most of the genetic characteristics of sheep A, she is not a true clone. Not all of an animal's genes are found in the cell's nucleus. There are a few dozen genes that reside in the mitochondria outside the nucleus in the cell's cytoplasm. In Dolly's case, some of these genes were supplied by the donor egg of sheep B.

The creation of Dolly represents a unique advance for cloning technology, but it inevitably intensified the debate about subjecting humans to cloning. Rather than a prelude to human cloning, however, many scientists herald the achievement as the forerunner of a revolution in animal breeding that will allow the highest quality farm animals to be produced and will provide a cost-effective method of producing medicines for human use. Cloning may also be used to create genetically altered animals capable of providing major organs for surgical transplantation into human beings.

The impact of this material has had on :

Economy: Because it's an expensive project to realize, it is hard and complicate so before they made their first discovered they were spending money to study it to find how to do it.

Lifestyle: Because we have the possibility to duplicate ourselves, to have our own clone, a lot of people don't like the idea because it's not natural.

Environment: Yes because these people are trying to be God by giving life.

Products: The new technologies help these people to realize more discoveries and maybe one day we can buy our own clone. So each day these technologies are better.


Of course in my opinion this discovery has benefited society, because now we know that we have the opportunity to be God, to create more animals and plants and humans.

With this discovery we learned more about us and about how detailed and complicated the human body is.

I learned with this discovery that each day the humans discover more and more things that we never imagined could be possible.

Enviado por:Kwensa
Idioma: inglés
País: Estados Unidos

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