Cloning
Cloning refers to making a copy of DNA, either the entire genome or just a piece of it. Cloning a fragment of DNA containing a gene, or a part of a gene, is a common practice in many laboratories.

The desired section of DNA is isolated, and inserted into a vector molecule (commonly a plasmid) and then copied. Scientists can use the copies to study individual genes and their roles within the cell.

Using this technique, scientists can also create libraries of genes. These libraries, either cDNA or genomic, consist of clones of individual or small groups of genes. Genomic libraries are clones made directly from the gene on the chromosome, whereas cDNA libraries contain DNA that is complementary to the mRNA of the gene (hence, cDNA).

Whole organism cloning is done by taking an organism’s DNA, transferring it into a donor egg (without a nucleus), then allowing the egg (with its new DNA) to begin acting like a typical fertilized egg and dividing outside of a uterus. Then, the collection of cells is transferred into a surrogate mother, where the clone will develop and be delivered. The cloned organism will be genetically identical to the organism who donated the DNA.

Cloning animals in this way raises strong feelings for many people. At present, Australia and many other nations have decided not to allow human cloning.

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Thylacine Cloning:
The Thylacine, or Tasmanian tiger, is an extinct animal that was originally found in Tasmania. The Australian Museum has a newborn thylacine preserved in alcohol. Currently, there is much debate as to the future of the thylacine’s DNA. Some scientists want to try to clone the thylacine, using the Tasmanian devil as a host for the DNA. Others simply want to compare the thylacine’s DNA to that of similar animals, such as the Tasmanian devil. Current technology would make either task very difficult.

In 1999, the Australian Museum launched a program to analyse the feasibility of cloning the thylacine. They examined their own resources, as well as the possibilities of outsourcing the project. In 2005, the Australian Museum concluded that, while they possess the ability to create a library of DNA, they do not have facilities or funding for any further, necessary cell culture of the thylacine cells. The museum also determined that the DNA in the pup was too degraded to work with.

The prospect of cloning the thylacine, or any extinct animal, raises a number of ethical questions concerning human being’s ability to recreate and reintroduce an animal into a changed environment.

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Cloning: Serial Nuclear Transfer vs. Single Nuclear Transfer
Australian scientists at Monash University have successfully cloned a cow, called Brandy, using a new technique called Serial Nuclear Transfer (SNT). This has a few more steps than Single Nuclear Transfer.

In Standard Nuclear Transfer, a scientist takes a cell from an adult, and removes the nucleus, which contains the DNA. The nucleus is then injected into a donor egg cell that already has had its nucleus removed. The donor egg, with the new nucleus, is allowed to begin develop in vitro; outside of the uterus. Once the egg is shown to be viable, the egg is inserted into a host uterus, and pregnancy will continue as normal.

Serial Nuclear Transfer is similar to Standard Nuclear Transfer. The nucleus from an adult cell is put into an empty donor egg cell. Then this egg is fused with a recently fertilized egg (again, with the nucleus removed) in order to transfer the nutrients to the clone. This gives the cloned egg a better chance of surviving. Once the fusion has occurred, the egg cell is implanted into the host female.

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Epigenetics
Epigenetics is a relatively new field in molecular biology that refers to all modifications to genes other than changes to the sequence of DNA base pairs. An example of an epigenetic modification is the addition of molecules (like methyl groups) to the DNA backbone. These additions alter the structure of the DNA molecule and how it interacts with other molecules in the cell.

Sometimes, two people can share the same genotype (the gene sequence is identical) but have a different phenotype (the outward appearance is different). This is caused by the regulation of genes, by turning genes on and off usually through methylation (addition of a CH3 group) to cytosine. Many traits show epigenetic effects, such as hair colour, eye colour and skin colour.

The occurrence of methylation explains why cloning will not always produce an identical individual. If the donor DNA carries the genes for brown hair, the shades of brown will vary between the original donor and the clone. Fingerprints are always unique to individuals, even theoretical human clones.

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