Hi everyone:)
Dolly was the first mamal cloned from an adult somatic cell that played the role of the DNA-donator. Nuclear transfer enabled scienticst to transfer DNA into several egg cells, from which only a few survived. The Researchers were making it able for Dolly to own the identical DNA as their DNA donator by taking the surving ones.
Nuclear transfer
An enucleated egg cell (an oocyte, cell which has it's nucleas removed) gets an nucleous from a another somatic cell inserted. As the nucleous of a somatic cell contains the DNA of the donator from which it was taken, an embryo can develop that later conatins the same DNA as the one from the donator: a clone has been made. The procedure was conceived in 1928 by German embryologist Hans Spemann, who also won the Nobel Price in Physiology or Medicine in 1935. As easy as the fusion of the two sounds, it can only be achieved by preicse work under a microscope and due to the stress put on the cells, many of them just die before an embyro develops.
"Dolly"
The sheep with three "mothers", of which one carried the embyro, one gave the scienticst the somatic cell and one the unfertilised egg cell, was born on 5 July 1996 as a result of experiments of the Roslin Institute. By using electrical pulses, the scienticsts were able to fuse the nucleous of the somatic cell with the egg cell. After they were sure the cell was dividing normally, they inserted it into another Scottish Blackface ewe, which carried the embryo. As the egg cell was taken from an Scottish Blackface sheep, they could already see the success of the cloning, because the DNA of the somatic cell contained information for a white face as it was taken from a six-year-old Finn Dorset sheep. Even though, Dolly wasn't the first mamal ever cloned, she was very important for science, getting more knwoledge about genetics and more methods of producing medicine.
detailed illustration of the process of cloning Dolly
Animals before Dolly
Sheep, frogs were cloned some years before Dolly was cloned, but Dolly was different, having the DNA from an adult cell instead of an undiffered one. Taking an already specified cell, e.g. a liver cell, works as good as taking a skin cell. The part were Dolly differs from her DNA donator are the mitochondria (energy production of the cell takes place here). These were inherited from the egg donator sheep.
Dolly (shown above) later suffered from athrithis and a lung tumor common among sheep
Cloning sheeps for medicine
Tracey, a sheep which was sold for 15 million euros, was able to produce milk that contained the protein alpha-1-antitripsin. The protein is necessary for the normal lung function and could only be taken from blood perservees. The human gene was set into the DNA of the sheep, where the promotor for the gene is only active in the mammary gland, so it can't be found anywhere else in the sheep. This process is called "gene pharming" and helps people with diseases.
Controversy
The cloning was hardly discussed in the world. People claim that genetic engeneering is like playing God and directly is against the natural diversity spread by the new randomly created DNA, a new child is carrying inside his/her cells. Even today, it is always an ethical discussing how far science should go in case of cloning. We often hear terms like "designer babys", formed by the individual vision the parents have for the child.
Conclusion
Cloning is a very special thematic. On the one side it provieds us more informations about how our life works, on the other hand, it is very ethically discussed. If were are ablte to find a way to combine these two ways, people look at the topic, I hope we can find a solution that brings our world no disatvantages
SourcesTexthttp://www.animalresearch.info/en/medical-advances/timeline/cloning-dolly-the-sheep/http://theconversation.com/dolly-the-sheep-and-the-human-cloning-debate-twenty-years-later-63712http://www.heraldscotland.com/news/14595633.Two_decades_on__Dolly_the_sheep_still_remains_a_source_of_controversy/https://en.wikipedia.org/wiki/Dolly_(sheep)https://en.wikipedia.org/wiki/Nuclear_transfer
Pictureshttps://openi.nlm.nih.gov/imgs/512/27/280727/PMC280727_1477-7827-1-83-2.pnghttps://media1.britannica.com/eb-media/10/70110-004-A5E92641.jpghttps://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcSzpjeyMA4mdQPQclpnQZZ8VwqjGQ7cVvtLXFd9hO9geJ9E-Lax