Human Cloning Assignment

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Haretha Aydi

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Human Cloning Assignment


In this assignment, we are to choose a specific subject and write out and argument with and against it. We should also include background information and carry out a research on that specific topic, lastly a conclusion should be set out.

Background Knowledge:

)- Human cloning:

First explored by Spemann in the 1920's to conduct genetics research, nuclear transfer is the technique currently used in the cloning of adult animals. A technique known as twinning exists, but can only be used before organism's cells differentiate. All cloning experiments of adult mammals have used a variation of nuclear transfer.

Nuclear transfer requires two cells, a donor cell and an oocyte, or egg cell. Research has proven that the egg cell works best if it is unfertilized, because it is more likely to accept the donor nucleus as its own. The egg cell must be enucleated.

The nucleus is removed from the egg cell This eliminates the majority of its genetic information. The donor cell is then forced into the Gap Zero, or G0 cell stage, a dormant phase, in different ways depending on the technique. This dormant phase causes the cell to shut down but not die. In this state, the nucleus is ready to be accepted by the egg cell. The donor cells nucleus is then placed inside the egg cell, either through cell fusion or transplantation. The egg cell is then prompted to begin forming an embryo. then, the embryo is then transplanted into a surrogate mother. If all is done correctly, occasionally a perfect replica of the donor animal will be born.

Each group of researchers has its own specific technique. The best known is the Roslin technique, and the most effective and most recently developed is the Honolulu technique.

The cloning of Dolly has been the most important event in cloning history. Not only did it spark public interest in the subject, but it also proved that the cloning of adult animals could be accomplished. Previously, it was not known if an adult nucleus was still able to produce a completely new animal. Genetic damage and the simple deactivation of genes in cells were both considered possibly irreversible.

The realization that this was not the case came after the discovery by Ian Wilmut and Keith Cambell of a method with which to synchronize the cell cycles of the donor cell and the egg cell. Without synchronized cell cycles, the nucleus would not be in the correct state for the embryo to accept it. Somehow the donor cell had to be forced into the Gap Zero, or G0 cell stage, or the dormant cell stage.

First, a cell (the donor cell) was selected from the udder cells of a Finn Dorset sheep to provide the genetic information for the clone. For this experiment, the researchers allowed the cell to divide and form a culture in vitro, or outside of an animal. This produced multiple copies of the same nucleus. This step only becomes useful when the DNA is altered, such as in the case of Polly, because then the changes can be studied to make sure that they have taken effect.

The donor cell is grown in a petri/culture dish.

A donor cell was taken from the culture and then starved in a mixture which had only enough nutrients to keep the cell alive.

This culture dish barely has enough nutrients to keep the cell alive.

This caused the cell to begin shutting down all active genes and enter the G0 stage. The egg cell of a Blackface ewe was then enucleated and placed next to the donor cell. One to eight hours after the removal of the egg cell, an electric pulse was used to fuse the two cells together and, at the same time, activate the development of an embryo.
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The enucleated egg cell and the mammary cell are fusing together.

This technique for replicates the activation provided by sperm is not completely correct, since only a few electrically activated cells survive long enough to produce an embryo.

If the embryo survives, it is allowed to grow for about six days, incubating in a sheep's oviduct. It has been found that cells placed in oviducts early in their development are much more likely to survive than those incubated in the lab. Finally, the embryo is placed into the uterus of a surrogate mother ewe. ...

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This is a very well researched report that covers the science surrounding cloning well. 1. The sources of information need to be included and an indication method used. 2. There are several comments that display bias. Opinions need to be indicated as such. 3. The inclusion of primary information sources is excellent, but they should be referenced. ****