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9.7 Option - Genetics: The Code Broken? : 5. Gene therapy

Extract from Biology Stage 6 Syllabus (Amended October 2002). © Board of Studies, NSW.
[Edit: 12Jun 09]

Prior learning: Stages 4 and 5 Science, 5.8.2 c) and d)

HSC 9.3.3 and 4

process and analyse information from secondary sources to identify a current use of gene therapy to manage a genetic disease, a named form of cancer or AIDS

• When you have information from your teacher, the information below in the next dot point or other secondary sources, you could process this information by comparing information from different sources. Extract the information that you think best allows you to identify your chosen current use of gene therapy. Be aware that you only have to choose one from the three listed above.

What is the current status of gene therapy research? Human Genome Project Information, US Dept of Energy
Scroll down to 'What are some recent developments in gene therapy research?' for more information on gene therapy.

• Analyse the information that you have.

describe the current use of gene therapy for an identified disease

• Gene therapy is the process of replacing defective genes with normal genes. This is done by cutting genes from the DNA of healthy cells and inserting them into the DNA of defective cells and tissues.
   
• The transfer of large genetic sequences into cells is problematic because DNA is a negatively charged molecule and will not easily cross cell membranes. To overcome this problem, scientists are producing vector systems, in particular viral vectors, for transporting genes into cells. This allows genes to be cut from the healthy DNA in one cell and inserted into the DNA in another defective cell.
   
• Cystic fibrosis is caused by a recessive gene, that does not allow sufferers to produce a protein that controls the movement of ions across cell membranes. This results in thick mucus accumulating in the lungs, which can cause frequent lung infections and lung damage and destruction. This leads to shortness of breath and the life expectancy of sufferers is considerably reduced. Gene therapy is being trialled as a possible cure for cystic fibrosis.
   
• The gene therapy for cystic fibrosis involves replacing the defective gene with a healthy one in body or somatic cells of the adult. Normal human genes are first cloned in bacteria and then inserted into adeno-associated viruses that have been made harmless. These viruses are used to transfer and insert the healthy gene (segment of DNA) into defective lung cells by putting them in a solution and dripping them into the lung through a thin tube. The virus enters the lung cell nucleus and inserts itself into the human DNA. The lung cells can then function normally.
   
• Other diseases that are being trialled with gene therapy cures include bone marrow disorders, Huntington’s disease, AIDS and some forms of cancer.

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