Monday, 12 March 2012

What was the purpose of cloning dolly the sheep?

The purpose was not the act of cloning dolly itself, but rather the implications that came as a consequence of the knowledge that we could employ recombinant DNA technology in living organisms to create a clone.

An example of recombinant DNA technology in organisms being put to commercial and productive use is to breed animals (i.e. cows or other dairy - producing livestock) that due to changes in the genetic coding, are able to produce hormones and/or other useful chemicals for humans (insulin, for example, could be produced naturally in the cow's milk) - this genetic trait might occasionally be passed onto offspring naturally, reducing the need to repeat this process.

Monday, 5 March 2012

5.13, 5.14, 5.15


5.13a Recombinant DNA

Bacteria: Plasmids are found in bacterial cells – ring of DNA
Virus: Protein shell (capsid) -> Nucleic acid inside (DNA/RNA) ONLY THESE COMPONENTS

Human Chromosome -> Length of DNA -> Gene which represents the protein INSULIN which is a hormone that controls blood sugar levels

1.     Restriction enzyme: ‘cuts’ out insulin gene from DNA
2.     Plasmids from bacteria cut with SAME RESTRICTION ENZYME-> ring structure broken
3.     Insulin gene introduced to cut plasmid
NOTE: plasmid and gene both DNA - compatible
4.     Insulin joins plasmid DNA with LIGASE ENZYME

This is known as ‘recombinant DNA’

5.13b Recombinant DNA

Virus: Protein shell (capsid) -> Nucleic acid inside (DNA/RNA) ONLY THESE COMPONENTS

To transfer recombinant DNA into host cell (virus shell):
1.     Remove nucleic acid from virus so only capsid remains
2.     Recombinant DNA taken up by capsid and becomes known as a VECTOR

RC DNA -> Vector -> Host Cell

Why virus?
Virus (phage) infects bacterial cells
è Attaches to cell membrane of bacteria
è RC DNA into bacteria

NEW Bacteria Host known as TRANSGENIC (genes transferred from another organism)
-       Contains both RC DNA and Bacterial DNA

5.14 Humulin

Bacterial cell (i.e. e-coli) contains RC DNA & bacterial DNA -> transgenic
è Culture (large population) of bacteria injected into fermenter

For optimum production (enzymes) must regulate:
pH
Temperature
Air (aerobic)

Provide: Nutrients
The bacteria culture will then manufacture insulin protein from nutrient provided
Remove product (insulin + others) and purify for human use: known as DOWNSTREAM PROCCESSING
-> Genetically engineered insulin (produced by RC DNA) known as HUMULIN

5.15a Genetically Modified Plants

Maize: damaged by pests -> loss of crop yield
Bacteria (Bt): Bt chromosome contains gene produces Bt toxin which kills the pests attacking the Maize
è How do we get this chromosome into the Maize?

1.     Restriction enzymes -> cut out gene for Bt toxin from bacteria
2.     Introduced to cells of Maize plants
è Gene gun: particles of gold coated in Bt gene
è Fired at high velocity at plant cell
è Bt gene is introduced to interior of plant cell
è Maize cells produce Bt toxin
3.     Pests are killed = resistance = higher crop yield