Cellular Metabolism and Reproduction: Mitosis and Meiosis 85
Common Disease, Disorder, or ConditionGenetic DisordersTay-Sachs Disease^
Tay-Sachs disease (TAY SAKS) is caused by a genetic recessive trait found mainly in
Jewish families of eastern European origin, especially the Ashkenazic Jews. It is a
neurodegenerative disorder of lipid metabolism caused by a lack of the enzyme
hexosaminidase A, resulting in a buildup of sphingolipids in the brain. This causes
progressive physical and mental retardation resulting in an early death of the af-fected
individual. Symptoms first appear by 6 months of age with convulsions, followed by
blindness due to atrophy of the optic nerve, dementia, and paralysis. Children usually
die between the ages of 2 and 4. There is no cure.
Klinefelter’s Syndrome^
Klinefelter’s syndrome (KLINE-fell-ters) occurs in males who have reached puberty. It
is caused by males who have extra X chromosomes. The most common condition is an
XXY chromosome. This condition results in long legs, small and firm testes, an
abnormal enlargement of the breasts, varicose veins, below normal intelligence, poor
social skills, and chronic pulmonary disease. Males with an XXXXY chromo-some have
severe congenital abnormalities and serious mental retardation.
Down Syndrome
Down syndrome is a congenital defect commonly caused by an extra chromosome 21.
It occurs in about one in every 600 to 650 live births in mothers who are 35 years of age
or older. It results in both mental retardation and physical defects. It was formerly
referred to as mongolism. The condition can be diagnosed by an amnio-centesis during
pregnancy. Some of the physical defects include a slant to the eyes, a low nasal bridge,
short broad hands with stubby fingers, broad stubby feet with a space between the first
and second toes, and abnormal tooth development. The most prominent feature of this
syndrome is mental retardation with IQ’s between 50 and 60. In addition, there can be
heart disease, chronic pulmonary infections, and visual problems. Those children who
sur -
vive their first few years tend to be stocky in
build and short with incomplete or delayed
sexual development.PROGERIA
Progeria is a congenital abnormality that causes
premature aging. During childhood, the
individual with this condition has wrin-kled skin
with graying hair. The person is of a small
stature with no facial or pubic hair and appears
very old looking. Death occurs around 20 years
of age.Kuvaev/Shutterstock.com Denis ©