Genetic Engineering

From ZuluNotes - Free Leaving Cert Notes

Genetic Engineering is also known as genetic manipulation or modification, recombinant DNA technology, gene splicing and gene cloning.

• Genetic Engineering is the artifical manipulation/alteration of genes.
• This process involves removing a gene (target gene) from one organism and inserting it into the DNA of another organism (like a 'cut-n-paste' process)
• The altered DNA is known as recombinant DNA. The organism containing the recombinant DNA is called a genetically modified organism (G.M.O.).
• If the DNA is transferred from one species to another, the organism recieving the DNA is said to be transgenic

Examples of this include:

1. A human gene inserted into another animal
2. A bacterial gene placed in a plant
3. A human gene inserted into a bacterium.
   

Process of Genetic Engineering:

Example: how a human gene (gene for insulin production) is inserted into a bacterium so that the bacterium can produce human insulin.

Process is as follows:

1. Isolation
2. Cutting
3. Ligation
4. Tranformation
5. Cloning
6. Expression

Isolation:

• Involves removal/isolation of the human DNA (or chromosome) and the bacteria DNA (which usually is a loop of DNA called a plasmid) from their cells. Plasmids carry on genes i.e. anitbiotic resistance.

Cutting:

• Both the human and bacteria DNA are cut with the use of a restriction enzyme (a type of enzyme which cuts DNA at a specific base sequence).
• The cut sections of human DNA are mixed with the opened bacterial plasmid, allowing the human DNA to be inserted into a plasmid.

Ligation:

• Ligation is the process by which the exposed ends of human DNA and plasmid DNA are spliced/joined together., using an enzyme called DNA ligase.
• The aim is for the target gene (the gene to produce insulin) to combine with the plasmid.
• Realistically, most of the combinations involve a plasmid bonding with another plasmid or with on or more sections of human DNA that don't have the target gene.

Tranformation:

• Transformation is the uptake of DNA into a cell. In this case bacterial cells are specially treated to enable them to take in plasmids.Only a few of the bacterial cells take in a plasmid. Even then, many plasmids don't contain a copy of the target gene.

Cloning:

• Growing the bacteral cells on agar containg an antibiotic identifies the cells containging plasmids. Only bacterial cells conaining a plasmid can grow. As the bacteria reproduce, so do the number of plasmids. The plasmids are said to be cloning vectors (they are the cloning gene).
• Many colonies (clusters) of bacteria grow on the agar, but only some of these colonies contain plasmids with the target gene.
• These colonies are identified using radioactive probes, which are the sections of DNA that are complementary to the target gene.
• Once the bacteria containing the target gene are identified, they are removed and cloned (grown) on fresh agar.

Expression:

• Expression is the creation of the desired product from the GMO (Genetically Modified Organism - in this case bacteria.)
• The bacteria with the target gene are grown in bioreactors with the correct 'food', temperature, pH etc. and allowed to form the product (such as insulin). This is an example of biotechnology.
• The product is isolated from the liquid and bacteria in the bioreactor, often involving difficult filtrations. The product is then purified for distribution.

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