Unformatted text preview: ible. The question
is, if one of your parents develops the disease, do you then wish to know whether you carry the dominant allele? Frequency = 1/20,000 live births.
***Marfan Syndrome (154700): Of interest because of the multiple (pleiotropic) effects of a single abnormal
allele. Affected individuals are very tall, have long fingers and toes, have abnormally flexible joints, tend to be
nearsighted, and have weakened cardiovascular systems. These characteristics result from a defective form of
fibrillin, an important component of connective tissue. Because of their height and flexibility, individuals with
Marfan Syndrome tend to excel in sports such as basketball and volleyball, but they are also at risk for ruptures of
the heart or aorta due to the weakened state of the connective tissue. Both Hank Gathers, a Loyola Marymount
basketball player, and Flo Hyman, a U.S. olympic team volleyball player, died of heart failures on the court due to
Marfan syndrome. Frequency = 1/10,000 in all ethnic groups.
***Neurofibromatosis (162200): The course of this unfortunate genetic disease involves the development of
hundreds of non-malignant tumors over the entire body. In combination with abnormal bone growth, the victim of
NF may be grossly deformed. The gene responsible for NF has been cloned and found to code for a tumor
suppressor gene. Tumor suppressor genes are involved in the regulation of cell growth and/or division, and as might
be expected, mutations in tumor suppressors are associated with a variety of different cancers. The unusually large
size of this gene (over 350,000 b.p.), and the fact that over half of NF cases are the result of new mutations, have
hindered attempts at developing effective prenatal screening strategies. There is no known cure for NF which
occurs with a frequency = 1/3500 live bi...
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