• Applications of genetic engineering include:

• Producing human insulin in bacteria.

• Gene therapy to cure genetic diseases.

• Increasing yields with transgenic salmon.

• Growing insect-resistant plants.

• Escherichia coli is a bacterium found in the human colon and often used in genetic research.
An E. coli cell often contains one or more plasmids, circles of DNA capable of replicating outside of the main bacterial chromosome, and not packaged in a protein coat.

• A restriction enzyme is an endonuclease that cuts DNA molecules at specific restriction sites that contain a palindrome sequence.

One restriction enzyme is EcoRI, which cuts DNA to produce fragments with complementary single-stranded "sticky ends".

DNA from different sources may hydrogen-bond their sticky ends.

DNA ligase fills in the gaps, yielding recombinant DNA.

Review:

• Producing recombinant DNA

1. A restriction enzyme cuts the source DNA at specific sites, cleaving the DNA into fragments, each with "sticky ends".
   
   
   
   
   
   
   
2. A vector such as a plasmid cut with the same restriction enzyme is combined with fragments of source DNA (containing the gene of interest) to form recombinant DNA.

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• The recombinant plasmids are inserted back into bacteria.
Bacteria are grown to produce clones - colonies of genetically identical cells.
The clone containing the gene of interest is selected for mass production.

• The polymerase chain reaction (PCR) consists of three steps:

1. Denaturation: separate the double helix by heat.

2. Primer annealing: single-stranded complementary DNA primers bind to denatured DNA.

3. Primer extension: DNA polymerase copies the target DNA using a pool of nucleotides.

Each cycle doubles the original target DNA.

20 cycles yield a million-fold in vitro amplification of the target DNA.

Review:

• DNA fragments can be separated as they move through a gel electrophoresis apparatus.
The negatively charged DNA fragments move at different speeds, based mainly on fragment size, toward the positive anode.
The separated fragments can be visualized with dyes or fluorescent light.
Review:

• DNA fingerprinting

DNA samples are cut by restriction enzymes to yield many fragments.

Different DNA sources yield different fragment patterns.

These fragments are separated by gel electrophoresis to identify individuals.

These 2 gels show that DNA from the rapist's semen matches that from the suspect's blood.

Review:

• How can DNA samples from a crime scene be amplified to have enough DNA for fingerprinting?
  • Use PCR.

    

• A mature mRNA, which contains only exons, is used as a template to hybridize a single strand of complementary DNA (cDNA) using reverse transcriptase.

DNA Polymerase is then used to make double-stranded cDNA, which is free of introns.

Review:

• Genetic engineering applications

1. Production of human hormones in bacteria and mice.

2. Creation of vaccines to combat infections.

3. Replacement of defective genes by gene therapy. Exercise

4. Genetically engineered hormones in "pharm" animals.

• The hormone insulin can be produced in bacteria to treat diabetes.

• Transgenic mice have been engineered to contain human growth hormone (HGH) in its genome.

The mice now produce the hormone which can be harvested to treat dwarfism.

• Piggyback vaccine

A gene encoding a harmful viral protein (Herpes simplex) is put into the DNA of a harmless virus (cowpox).

This piggyback vaccine is injected into the body.

The viral protein elicits antibody production, which confers protection from future infection by the harmful virus.

• The genetically engineered hormone bovine somatotropin (BST) became commercially available in 1994 and is injected into cows to enhance milk production.

• Genetically modified (GM) plants

• Pest resistance.
  
  
  
  
  
  
  
• Herbicide resistance.
  
  
  
  
  
  
• More nutritious crops.

• Bt is a pesticide derived from A bacterium (Bacillus thuringiensis) that has been genetically engineered into GM plants such as corn to confer pest resistance.

• These petunia plants were exposed to the herbicide glyphosate (Roundup).
The two on top were genetically engineered to be resistant to the herbicide.
The two dead ones at the bottom were not.