Cloning

What are clones?
A clone is a group of genetically identical organisms or a group of cells derived from a single parent cell.

Ethical Issues
They must be separated into reproductive cloning and therapeutic cloning.
Reproductive cloning = Dolly the sheep. Humans = twins...
Therapeutic cloning involves the isolation of stem cells
Foetal stem cells are often harvested from unused IVF embryos
These have the potential to be of great medical benefit. e.g. healing burns, heart tissue post cardiac arrest, kidney damage

Discuss the ethical arguments for and against the cloning of humans (4)
There are many arguments against the cloning of humans. For example, it's not our role as people to do this and some might say that we are tempting higher powers. It is also a very costly process and the consequences of cloning humans aren't known. Some clones may also show premature aging of have other health problems as a side effect. Some reasons for cloning may also be bad, for example, to replace a deceased family member.

However, there are some benefits to cloning. Cloned embryos can be used for further health research. Twins are also a form of cloning.

Outline a basic technique for gene transfer involving plasmids (5)
Gene transfer involves using restriction endonuclease to remove the plasmid, a circular ring of DNA from the bacteria. This leaves the stick ends at the end of the plasmid which are unattached hydrogen bonds. The donor is cut using the same restriction enzyme so that DNA ligase enzyme can join the sticky ends together. This is known as the recombinant plasmid. The cells are then replicated.

Outline a technique for transferring genes between species (5)
The gene that is required is cut out using restriction endonuclease. The plasmid is cut open with the same restriction enzyme. This gene is inserted into the plasmid using DNA ligase that splices the sticky ends together. This is called a recombinant plasmid. The plasmids are inserted into new host cells suc as bacteria or viruses.

4.4.1. Outline the use of polymerase chain reaction (PCR) to copy and amplify minute quantities of DNA. 

• PCR is the cloning of DNA 
• Copies are made and the amount of DNA can be rapidly increased. This is useful if the source of DNA is small.
• Temperature is used instead of enzymes like helicases (95˚C)
• DNA polymerase is thermostable to protect it against the reaction temperatures.
• This is an automated process and can produce sufficient DNA in 20 cycles.
• It is a laboratory technique that is used to solve a simple problem: how to get enough DNA to be able to analyze it. 
• By using PCR forensics experts or research technicians can obtain million of copies of the DNA in just a few hours. 
• Such quantities are large enough to get results from, notably using gel electrophoresis.

Gene Transfer

Gene transfer is the technique of taking a gene out of one organism and placing it in another organism.


4.4.8. Outline a basic technique for gene transfer involving plasmids, a host, restriction enzymes and DNA ligase.

Cutting and pasting DNA
Restriction enzymes called endonucleases are used to cut out the gene that needs to be transferred. If both the beginning and end of a gene are cut, the gene is released and can be removed from the donor organism.

DNA ligase is used for pasting genes as it recognizes the parts of the sticky ends and attaches them together.

DNA Cloning
A host cell is needed in addition to those two enzymes. Although yeast cells can be used as host cels, E. coli is most popular.  Plasmids are small circular DNA molecules found in bacteria, and can be cut with the same restriction enzyme. This leaves the sticky ends in the plasmid, which are, effectively, unattached hydrogen bonds. The plasmid can be cut at particular sites called the restriction sites. To copy a gene, it has to be glued into a plasmid.

The gene is pasted into the plasmid using DNA ligase. The plasmid is now called a recombinant DBA and it can be used as a vector.

The vector is placed inside the host bacterium and the bacterium is given ideal conditions to grow. This is done by putting it into a bioreactor. This process has been used to make human insulin.

4.4.10. Discuss the potential benefits and possible harmful effects of one example of genetic modification.

Benefits of GMO:

1. Increase yields in regions of food shortage
2. Yields crop with specific dietary requirement such as vitamins and minerals
3. Crops that don't spoil easily
4. Farmers can be in control of what crops or livestock they produce.
5. Multinational companies who make GM plants claim they will enable farmers in developing nations to reduce hunger by using pest-resistant crops or GM plants which require less water.

Harmful effects

1. No one knows the long term effects of GMOs in the wild. Genes from GM plants could be integrated into wild species giving them an unnatural advantage over other species and an ability to take over the habitat.
2. Bt-crops which produce toxins to kill insects could be harmful to humans.
3. Risks for allergies: could be allergic to GM tomatoes.
4. Critics are worried that large portions of the human food supply will be the property of a small number of corporations.
5. High-tech solutios are not necessarily better than simpler solutions. Crop production could be increased by teaching farmers how to use water and natural pest-control systems more efficiently.
6. A proliferation of genetically modified organisms may lead to a decrease in biodiversity.