health

Cystic fibrosis is primarily a disease of people of northern European
ancestry; in fact it is the most common fatal inherited disease among
Caucasians in the United States, affecting one child in every 3,200. CF
affects one in every 9,200 Hispanic children, one in every 15–17,000
African American children, and one in every 31,000 Asian American
children. As of 2008, there were about 30,000 people with CF in the
United States and about 70,000 in the world.
Males and females are equally likely to be born with CF; however,
females are more severely affected and tend to die at younger ages.

Tay-Sachs Disease (TSD)

TSD is another fatal inherited disease. It is
caused by a genetic mutation in the HEXA gene
on chromosome 15. It occurs in one in every
320,000 newborns in the United States. A
normal HEXA gene helps to produce an
enzyme that prevents a fatty substance called
GM2 ganglioside from building up in the nerve
cells of the brain. Without the enzyme, the
child’s brain cells begin to deteriorate and die.
Children with TSD seem to develop normally
until they are about six months old. They then
begin to lose their mental functions. By age
two, most children with TSD develop seizures,
become blind, paralyzed, and unable to
respond to their parents. They usually die
around age five. As with cystic fibrosis, there is
no cure for TSD.
TSD is inherited in the same pattern as cystic
fibrosis; that is, both parents must have an
abnormal HEXA gene for their child to be born
with Tay-Sachs. About one person in every 250
in the general American population is a carrier
of TSD. However, the defective gene is much
more common among Jews of Eastern European
descent (one in every twenty-seven) and
French Canadians (Cajuns) living in Louisiana
(one in every twenty-five).