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inexpensive to screen, if detected early it can be effectively treated by periodic phlebotomy (blood letting). Hemochromatosis is a major public health problem only because of lack of awareness by the public and health
***Phenylketonuria (261600): Another enzyme deficiency. In this case the homozygous recessive individual
cannot convert phenylalanine to tyrosine, an important amino acid. The result is the accumulation of phenylketones
in the blood and in the brain where they cause mental retardation. Tested for at birth, treatment is primarily dietary
for at least the first 8 years of life, until the brain completes its development, although recent studies indicate that
dietary relaxation after this time can be associated with significant reduction of cognitive abilities. Frequency =
1/10,000 worldwide, but is more common in persons of Scottish and Irish decent, and the mutation is believed to be
of Celtic origin. ***Sickle Cell Anemia (603903): This recessive disease occurs primarily in persons of African and Mediterranean
heritage. It is unusual in that the homozygous genotype results in a very serious and disabling disease (sickle cell
anemia), but there is actually selection for the mutation because heterozygous carriers have significantly increased
resistance to malaria, an advantage for those who live in the malaria belt of North Africa and the Mediterranean. Frequency in U.S. blacks = 1/500 live births.
Tay-Sachs (272800): An enzyme deficiency disease which results in the accumulation of gangliosides (lipids
produced in the nervous system). The afflicted baby is normal for the first few months, then goes rapidly downhill,
losing vision, mental cognition, and muscular control. Usual life span is 2-4 years. Frequency = less than 1/100,000
live births in the tot...
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