5.15a Genetically Modified Plants

Key Points:
1. Maize can be damaged by the larvae of the European cork borer. This can cause up to 20% loss of crop yield.
2. The existance of a bacterium called BT, one of the chromosomes contains a gene which produces BT toxin. This is known to kill the cork borer larvae.
3. The first step is to take a restriction enzyme and cut out the gene of the BT which produces the toxin. This has to be transferred to the cells of the maize plant. This isnt easy. The technique which is being used is to use a gene gun and fire tiny pieces of gold covered with the BT gene and firing them at high velocity into the plant. This makes the maize cells contain BT. Kills larvae. Gives the maize resistance to damage caused by the cork borer.

5.14 Humulin

Key Points:
1. In 5.13b we saw the making of transgenic cells using a virus capsule and a bacterial cell.
2. A culture of this bacteria will be put in a fermenter and this culture will need to be provided with nutrient, temperature and pH and the gases which are in the chamber. By creating the optimal temperature, the population will increase and the bacteria manufacture more and more insulin.
3. The product will then be removed and then purified. There are many purifications needed to make it safe for humans. Called downstream processing. Humulin.

5.13b Hosting recombinant DNA

Key Points:
1. In 5.13a Recombinant DNA was introduced. It is a mixture of the human gene and the bacterial plasmid.
2. Inside a virus is the nucleic acid (DNA or RNA) and around this is the protein shell. The first thing to do is to remove the RNA from the virus. The capsid is all that is required. The plasmids are taken up by the virus and the virus will act like a vector
3. This will help transfer the DNA into the host cell. The reason for this is that this virus is known as a phage, and this infects bacterial cells. The virus will attach itself to the cell membrane of the bacteria and insert the DNA into the host cell. At the end of this process, there is a bacterial cell which contains the recombinant DNA including the human gene for insulin. Transgenic.

5.13a Recombinant DNA

Key Points:
1. The image above represents a plasmid. Plasmids are found in bacterial cells, and they are a ring of DNA. Don't carry very many genes.
2. The diagram on the right shows a virus. Virus has a protein shell called a capsid, and inside there will be either DNA or RNA. No other cellular components.
3. The third diagram shows a human chromosome, this is a length of DNA. Chromosome is made of DNA. A gene picked, this one is a code for insulin.
4. The restriction enzyme is chosen and this will cut out the gene for insulin. Having cut the gene, a plasmid will also be cut with the same restriction enzyme. This leaves the plasmid looking like a broken circle.
5. The next stage is to introduce the human insulin gene. The gene will be inserted into the plasmid and this will be completed by adding a DNA ligase which will join the DNA onto the plasmid.

This combination is known as recombinent DNA.