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