Genetic Disorders Paper

This essay has a total of 672 words and 3 pages.

Genetic Disorders


Each year a number of children are born with biological defects that impair normal
function. For THREE of the following conditions, discuss such aspects as the biological
cause, the methods of treatment and possible means of detection and/or prevention.


One lethal disorder inherited as a recessive allele is Tay-Sachs disease. This is caused
by a dysfunctional enzyme that fails to break down brain lipids of a certain class. The
symptoms usually become manifest a few months after birth. Some symptoms are seizures,
blindness and degeneration of motor and mental performance. Death is the result of this
disease, in children. With Tay-Sachs disease, the brain cells of a baby are unable to
metabolize gangliosides, a type of lipid, because a crucial enzyme does not work properly.
As the lipids accumulate in the brain, the brain cells gradually cease to function
normally. Only children who inherit two copies of the Tay-Sachs allele qualifies as a
recessive. At the biochemical level, we observe an intermediate phenotype characteristic
of incomplete dominance: The enzyme deficiency that causes Tay Sachs disease can be
detected in heterozygotes, who have an activity level of the lipid-metabolizing enzyme
that is intermediate between individuals homozygous for the normal allele and individuals
with Tay-Sachs disease. Heterozygotes lack symptoms of the disease, apparently because
half the normal amount of functional enzyme is sufficient to prevent lipid accumulation in
the brain. In fact, heterozygous individuals produce equal numbers of normal and
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