What Is Huntington's Disease?
Huntington's disease (HD) is an inherited neurological
illness causing involuntary movements, severe emotional
disturbance and cognitive decline. In the United States alone,
about 30,000 people have HD. In addition, 35,000 people exhibit
some symptoms and 75,000 people carry the abnormal gene that
will cause them to develop the disease. There is no cure for
this fatal disease.
A single abnormal gene produces HD. In 1993, scientists
finally isolated the HD gene on chromosome 4. The gene codes
for production of a protein called "huntingtin," whose function
is still unknown. But the defective version of the gene has
excessive repeats of a three-base sequence, "CAG." In the
normal huntingtin gene, this sequence is repeated between 11
and 29 times. In the mutant gene, the repeat occurs over and
over again, from 40 times to more than 80.
This defect causes the resulting huntingtin protein to be
malformed, prone to clumping in the brain and causing the death
of nearby nerve cells. Cells of the basal ganglia, a brain area
responsible for coordinating movement, and of the cortex, which
controls thought, perception and memory, are most often
affected.
Health
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