16.1 Gene Therapy.

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What is gene therapy?
Replacing defective genes in one individual with genes cloned from a healthy individual.
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What causes cystic fibrosis?
A mutant recessive allele which causes 3 bases A-A-A to be deleted (deletion mutation). The normal gene, Cystic fibrosis trans-membrane-conductance regulator which normally produces 1480 amino acids is left one amino acid short.
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What is the result of the missing amino acid in cystic fibrosis sufferers?
The protein cannot perform its role of transporting Cl- ions across epithelial membranes.
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What is CFTR responsible for?
It is a chloride ion channel that transports Cl- out of epithlelial cells, and naturally water follows.
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What happens with the chloride ion channel in a cystic fibrosis sufferer?
The membranes are therefore dry and the mucus they produce is viscous and sticky.
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What are the symptoms of cystic fibrosis?
-Mucus congestion in the lungs (increased chance of infection), breathing difficulties (less efficient gaseous exchange), accumulation of thick mucus in pancreatic ducts causes formation of fibrous cysts. Accumulation of thick mucus in sperm ducts.
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What is the allele for cystic fibrosis?
Recessive.
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List 2 treatments of gene therapy and what they involve?
1. Gene replacement (defective gene replaced by healthy gene). 2. Gene supplementation (1 or more copies of healthy gene inserted alongside defective gene. Healthy genes are dominant so mask the recessive allele).
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Depending on what kind of cell is being treated there are two different types of gene therapy. What are they?
1. Germ line therapy - replacing/supplimenting genes in a fertilised egg so it passes on to future generations. 2. Somatic cell therapy - targets affected body cells so isn't passed on to future generations.
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Describe the use of harmless viruses to deliver cloned cystic finbrosis trans-membrance-conductance regulator?
1.Adenovirus made harmless by interferring with gene. 2.Virus grown in a lab alongside plasmids with desired gene. 3. CFTR incorporates into DNA of virus. 4.Virus is isolated and purified. 5.Virus injects the DNA into epithelial cells of lungs.
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Why are genes wrapped in lipids?
Because that way they can easily cross the phospholipid bilayer.
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Explain how CFTR can be delivered using lipid molecules?
1. CFTR is isolated & inserted into bacteria plasmid, then bacteria, using gene markers to identify which ones have taken it up. 3.Bacteria cloned to produce multiple copies. 4. Plasmids extracted and wrapped in lipid molecules. 5. Liposomes made.
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How are the liposomes of CFTR delivered to the body?
Through spraying them into the nostrils of a patient, and they are then drawn in to the lungs in inhalation.
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Why are methods of delivering the CFTR gene not always effective?
1. Adenovirus might cause infections. 2. Patients may develop immunity to adenoviruses. 3. The liposome aerosol may not be fine enough to pass through bronchioles. 4. CFTR gene is very rarely expressed.
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What is severe combined immunodeficiency? (SCID)
a rare genetic condition where people who suffer do not have any immune system due to a defect in the gene that codes for adenosine daminase which destroys toxins that kill white blood cells.
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How do people with SCID survive?
In a bubble.
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How can gene therapy be used to help treat SCId.
ADA gene is isolated using restriction endonucleases. ADA gene inserted into retrovirus which is mixed with patients T cells. Retrovirus injects copy of normal ADA in to T cells. T cells reintroduced into patients blood to provide geneticcode for ADA
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Why does treatment for SCID have to be repeated?
Because T-cells only live for approximately 6-8 months.
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Other cards in this set

Card 2

Front

What causes cystic fibrosis?

Back

A mutant recessive allele which causes 3 bases A-A-A to be deleted (deletion mutation). The normal gene, Cystic fibrosis trans-membrane-conductance regulator which normally produces 1480 amino acids is left one amino acid short.

Card 3

Front

What is the result of the missing amino acid in cystic fibrosis sufferers?

Back

Preview of the front of card 3

Card 4

Front

What is CFTR responsible for?

Back

Preview of the front of card 4

Card 5

Front

What happens with the chloride ion channel in a cystic fibrosis sufferer?

Back

Preview of the front of card 5
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