Páginas: 8 (1831 palabras) Publicado: 13 de agosto de 2010

Everybody has heard about the term cloning and the history of Dolly, the cloned sheep. Due to its implications, cloning has become the most controversial topic of recent times. Many different opinions and beliefs, not only among the public in general but also among the scientist, make this theme a very interesting topic to be discussed.
In the following pages, a briefhistory of cloning, a description about the cloning procedure and some other aspect of cloning will be presented.
As mentioned before, many people have heard about the history of Dolly and think about this event as the beginning of cloning. But the history of cloning began long before Dolly.
In plants this process seems to be natural and quite of common. For example, the water hyacinthproduces seeds mostly by sending out underwater stems that after a while will transform into a new plant (Cohen, 1998). Natural cloning occurs in plants and even in trees that can become in a big forest. However, artificial cloning has also a long history that began at least four thousand years ago with the ancient practice of horticulture. This practice implied taking a twig or cutting from oneplant and either grafting it on another or rooting it to produce a new plant or shrub (Cohen, 1998). In now days, cloning fruits or vegetable is common. Cohen. D (1998) made reference to the apples on the supermarket and how they look. He mentions that some apples, specially the expensive ones are usually same size, same color, all of them look alike and this happened because theses apples arecloned. He concludes asking if biting on of these apples bothers us or if it should bother us.

From: From:
However, the process to create a clone of an animal is more recent and started with frogs. In 1952, the success was achieved with the cloning of frogs. A group of scientist from Philadelphia cloned the first frog embryo. They took the nucleusout of a frog embryo cell and replaced into a nucleus of an unfertilized egg cell. Frogs eggs are bigger than eggs from others mammals, are easy to find and abundant, that is why scientist decided to experiment with frogs. This was the first time that this process was use in an animal and it is still in use with some modifications in the method.From:
But the question was still remaining: it is possible to take the same step with higher animals, mammals or even from an adult animal. This challenge imposed by the scientific community led to the creation of several research groups in this field, trying to cloning in mice. The first successful experiments in genetic engineering took place in 1973 after beingcreated the first recombinant DNA molecule in laboratory (1972): genes from one species are placed into another species and work properly. But it took 20 years to move from basic research to applied technology successfully. In the 1980’s the failure was resounding. Scientists were still using the same experimental protocol, but the mice did not pass from the first stage of being embryos. As a resultof these failures, many scientists began to claim that cloning of mammals was impossible.
In 1986 Ian Wilmut was assigned to a project. The goal of the project was to look for a way to breed better sheep, genetically altered, that can produce a certain chemical in its milk that can be useful in making specific drugs.  They took cells from a sheep embryo of nine days, and instead of merging themimmediately, they put them in vitro to make them proliferate. The cells were resulting in five embryos that were implanted in the wombs of a different sheep. In this experiment three lambs were born prematurely and died and two grew normally: Megan and Morag. More research was done, and on July 5, 1996, Dolly was born, a lamb cloned from a frozen mammary cell from another adult sheep.  Some of...
Leer documento completo

Regístrate para leer el documento completo.

Estos documentos también te pueden resultar útiles

  • La clonacion
  • Clonacion
  • Clonación
  • Clonacion
  • clonacion.
  • La Clonacion
  • Clonacion
  • Clonacion

Conviértase en miembro formal de Buenas Tareas