Usually a dominant allele with such severe effects would be expected to occur only as a new mutation and not be transmitted to future generations. But because the onset of Huntington’s disease usually occurs between the ages of 30 and 50, an individual may have children before knowing whether he or she carries the allele. Genetic testing allows some persons who are at risk to determine whether they are carriers. Persons who test positive and do not have children will eventually cause a decrease in the frequency of the allele in the population. Not everyone who is a risk wishes to be tested because anyone who tests positive for the allele must then live with the knowledge that he or she will eventually develop the disease and die.
The trait is in each generation and equally distributed among males & females. Every child of an affected individual has a 50% chance of being affected and a 50% chance of being a carrier
Caused by a defective gene that disrupts the channel protein regulating the passage of chloride ions out of the body’s cells. Chloride ions are a component of table salt and are prevalent in the body. As a result of this disruption, chloride ions bulid up in the cells. Water then leaves the surrounding fluid and enters the cells by osmosis. This causes the fluid between the cells to become thick and sticky. The abnrmal buildup of mucus in the lungs and pancreas clogs airways and disables digestion. Therapy loosens and removes the mucus. Lung infections are the result of bacterial growth in the mucus. The CF gene is located on chromosome 7 and genetic testing is possible. Gene therapy is in the study phases. Routine CF testing is in the very near future.
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