Cloning is the process of creating a identical copy of a living being.
Early Cloning was embryo splitting which means that you take a very early stage embryo and separate the two cells from each other and then they both develop into identical copies of each other. This was first done by Hans Adolf Eduard Driesch in 1885. He did this by shaking a two celled sea urchin embryo until it split. Each embryo cell later developed into a fully grown sea urchin In doing this he proved that both cells in the embryo had a full set of genetic instructions. In 1902 Hans Spemann became the first person to perform artificial embryo twinning in a invertebrate. He split the two celled embryo using baby hair. This proved that complex animals also can be artificially twinned.
The first “nuclear transfer” was performed by Hans Spemann in 1928. He used baby hair to keep a part of the cytoplasm in a fertilized egg cell separate from the nucleus. After letting the cells split a couple of times he loosened the baby hair. Then he used the baby hair to separate the cell he had been working with. Both parts created grew into embryos. This was performed with a salamander embryo. This process is illustrated on the left.
Nuclear transfer is the technique that has been used in cloning from 1928 or 1952 depending on if you want to call the experiment above nuclear transfer. The basics of nuclear transfer is that you take a cell with all chromosomes separate the nucleus from it. Insert that nucleus into an egg cell that has had its nucleus removed. You then stimulate the egg cell so it thinks it has been fertilized. It then starts to divide in to a embryo which is placed in a surrogate mother if your goal is a fully grown cloned animal. You can also separate the embryo into single cells if you need a cell population for a experiment. This is illustrated in the bottom picture on the previous page.
Nuclear transfer development:
At first they did nuclear transfers with frogs because their eggs are very big in comparison to most species. This helped because they have an easier time seeing what they are doing. In the first successful tests scientists literally took the nucleus out of a somatic cell (a cell with all chromosomes) and put it inside an egg cell. The first thing they concluded from these tests was that the longer the donor embryo had grown for the more susceptible the clone was to mutations and missing body parts. They also definitely proved that the nucleus was responsible for growth and development of organisms.
In 1958 the first “real” cloning was done. The difference in this experiment is that instead of using an embryonic cell the scientists involved used an intestine cell of a tadpole which proved that fully grown cells still contain all the instructions to develop an organism. This experiment though is doubted as it is believed they used stem cells, stem cell are cells with no functions assigned to them which means they have not shut down any parts of the DNA yet.
J. Derek Bromhall did in 1975 prove that nuclear transfer is possible with mammal embryos. This was very useful as it was a step closer to human cloning and meant the agricultural business might invest money in cloning increasing the rate of development. His experiment was successfully done with a rabbit embryo as nucleus doner and resulted in a genetically identical embryo being created. He transferred the nucleus using a glass pipette. This was a very big break through because mammals egg cells are much smaller than frogs and invertebrates.
In 1984 the first fully grown mammal was created by nuclear transfer. This time they separated one cell from a 8-cell sheep embryo using chemicals and fused it with a sheep egg cell using electrical shocks. A few days after the creation of the embryo it was placed in a surrogate mother and as a result 3 lambs where born. This proved that mammals could be cloned successfully. This is still not actual cloning as it is still taking the cells from a embryo. This was performed by Steen Willadsen. In 1987 a cow was cloned using nearly the same technique used by Steen this was done by Neal First, Randal Prather, and Willard Eyestone.
In 1996 Ian Wilmut and Keith Campbell did something a bit different. Instead of using a embryo as their source of cells they used cells they had been keeping alive in the laboratory to create 2 identical sheep. Later this year these two men also managed to do the first real mammal cloning by creating Dolly(pictured to the right). This sheep was one of 277 attempts at creating a cloned sheep from fully grown somatic cells. This was done like the previously explained experiments just that the cells came from a fully grown sheep. This landmark sparked conversations about cloning and for the first time made the public interested in cloning and stem cell research.
After Dolly the process used for cloning has not changed significantly. The only big news that have happened after Dolly is the cloning of monkeys from embryos and cloning of genetically modified sheep to make their milk include certain vitamins like genom nine from humans. They also created the first male clone which was a mouse. They have also cloned endangered animals to try and save the species but then the problem of inbreeding starts to happen which means two recessive alleles have a higher likelihood of occuring in the population. In 2007 a monkey embryo was successfully created using nuclear transfer from a adult monkey. This had been tried for many years with no success before. The latest thing in cloning happened in 2013 when Shoukhrat Mitalipov and coworkers created a human embryo from baby skin cells and a lot of evidence was requested by the science community because of a scam in South Korea in 2004.
Cloning has been developed for many reasons today mostly to clone the perfect farm animals for maximal production. But in Germany during ww2 Josef Mengele did lots of tests on twins and people with physical differences like dwarfism in Auschwitz and after the war he fled to Argentina where historians think he managed to artificially make sure that twins were born. In this town 1 in 5 pregnancies result in twins, this number is usually 1 in 80. This was done with the end goal of a pure aryan race.
This has some ethical issues because some people think it is wrong to create living being artificially. Personally I think cloning is good until people start creating mass produced soldiers or other forms of mass production of people for own gain. I have no problem with my food being cloned and mass produced as long as the animals don’t suffer.