Cystic Fibrosis Thick mucous forms in the digestive tract and lungs of people with CF. As a result, they have difficult breathing and are susceptible to lung infections. The median life expectancy for babies born with cystic fibrosis is 37 years. The gene that causes the disease is on chromosome 7. One particular mutation of this allele causes 70-75% of the cases. It is somewhat difficult to detect prenatally. Gene therapy may be a possibility in the future. The normal gene was inserted into cells in laboratory cultures. Viruses have been engineered to deliver the gene. An aerosol spray is used to deliver the virus to the lungs. There has been some success reported in treating human patients in 1994. Cystic fibrosis is the most common lethal genetic disease among Caucasians in the US. One in 25 is a carrier; one in 2500 is affected. Tay Sachs A fatty substance builds up in the neurons (nerve cells) of people with Tay Sachs. This causes a gradual paralysis and loss of nervous function that leads to death by age 4 or 5. It is due to a single defective enzyme which normally digests the fatty material.
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