5.15a Genetically Modified Plants

1. Maize
- it is damaged by the larvae of the european cork borer. This causes 20% loss of crop yield.

2. In a bacterium that we will call Bt, there is a chromosome and on that chromosome there is a gene.
- when the gene is switched on it produces Bt toxin and this is known to kill the cork borer larvae.
- what can we do to get this toxin into maize to protect it from the european cork borer?

3. Take restriction enzymes to the gene of the Bt and chop the gene out
- so we only get the Bt gene for the toxin.

4. This is transferred to the cells of the maize plant.
- This is not easy and the technique used currently, involves a 'gene gun'.
- It involves taking tiny particles of gold, that is coated in the Bt gene, and firing it at a high velocity at the plant cell
- introduces the Bt gene to the interior of the plant cell. The Maize cell gets the gene and once switched on, it can switch on the Bt toxin --> killing the larve
- This gives the Maize resistance to damage caused by the cork borer.

5.14 Humulin

- the bacterial cell (E.Coli) has been transformed by the addition of recombinant DNA.
- the black circle, in the image, represents the plasmid DNA and the yellow dot, in the image, represents the human DNA (insulin gene in this instance)
- a culture of this bacteria (large population) will be injected into the fermenter.
- necessary to provide the culture nutrient, necessary to control the temp. and the pH and also the gases that are in the fermenting chamber.
- by creating the optimal temperature for bacterial growth, we will see this population increase and we will see the bacteria manufacture the protein insulin by switching on the gene for insulin.
- the bacteria inside the fermenter will manufacture the insulin protein from the nutrient provided (amino acids)
- it will be necessary to remove the product and carry out purification (many processes required for human use) - this is called Downstream processing
- the genetically engineered human insulin is called 'Humulin'

5.13b Hosting Recombinant DNA

- Recombinant DNA - mixture of human gene and bacterial plasmid
- it is necessary to transfer the structure into the host cell
- in this instance, the host is a virus and inside is the nucleic acid such as DNA or RNA and around it is the protein cell
- the first thing is: remove the nucleic acid from the virus. Only the capsid protein shell is needed
- the plasmids are taken up by the virus and acts as a vector recombinant DNA. It is going to help transfer the DNA into the host cell.
- the reason why we choose the virus is because the virus, known as the phage, infects bacterial cells.
- it is able to attach to the cell membrane of the bacteria and insert the recombinant DNA into the host cell.
- at the end of the process, we have a bacterial cell which now contains the recombinant DNA including the human gene for insulin.
- the bacteria has its own DNA plus DNA from another organism. This combination is known as 'Transgenic'

5.13a Recombinant DNA

1. Plasmind.
- they are found in bacterial cells
- they are a ring of DNA
- particularly small and dont carry many genes

2. Virus.
- it has a protein shell called a capsid and inside will be a nuclic acid. Possible DNA or RNA.
- it has no other cellular components. no cytoplasm, no nucleus, no other structures like this

3. Human Chromosome
- it is the length of DNA.
- the human chromosome is made of DNA
- the gene codes for the protein insulin which is a hormone controlling blood sugar levels

- the restriction enzyme is selected that can cut the DNA on two sides. Essentially, we are cutting out the gene for insulin
- the enzymes are called 'restriction enzymes'
- once the gene is cut, we progress to the stage where the plasmid is cut with exactly the same restriction enzyme
- this leaves the ring structure of the plasmid, broken.
- introduced into the cut plasmid, is the human insulin gene, remembering that the plasmid and the human gene is composed of DNA
- we leave the plasmid with the human gene inserted inside and necessary to complete the process by applying the second enzyme which is called the 'DNA ligase' enzyme which will join the DNA.
- this combination of the human gene and the plasmid DNA is known as 'Recombinant DNA'