James -
Quote:
> Can white people get Sickle Cell?
"Direct analysis of DNA to detect a mutant gene is possible for a
few diseases, but it relies on precise knowledge of the gene's
location and identity -- information that is only rarely
available. For example, sickle-cell anemia (of which 3,000 cases
are diagnosed each year in the U.S., mainly among blacks) can be
detected early in pregnancy by tests that examine DNA directly.
The test employs short, synthetic DNA 'probes,' radioactively or
chemically labeled for easy detection; they recognize and bind
specifically to the DNA at the site of the disease-causing
mutations, in this case the gene for one of the components of
hemoglobin. If a sickle-cell mutation is present, the probe for
the normal gene binds poorly. Alpha-1-antitrypsin deficiency,
beta-thalassemia and phenylketonuria (PKU), a metabolic defect
that can cause brain damage, can also be detected directly by
labeled DNA probes." --- Scientific American 257(2):30-31,
August 1987
"A new test for genetic defects in fetuses is generally safe and
accurate and the risks are barely greater than those of
amniocentesis, which is performed later in pregnancy, a
nationwide study concludes. // The major advantage of the new
method, called chorionic villi sampling, is that it can be
performed in the first trimester. This gives women the option of
a much safer and simpler {*filter*} if the test indicates genetic
defects. /.../ Doctors using chorionic villi sampling remove a
small bit of tissue from the developing placenta, typically with
the help of a slender, flexible tube threaded into the uterus
from the {*filter*}. /.../ Amniocentesis uses a needle inserted
through the abdominal wall to sample cells in the amniotic fluid
surrounding the fetus. // Doctors perform amniocentesis each
year on more than 150,000 pregnant American women, typically
those in their mid-30s or older whose babies are more likely to
be born with genetic defects. It is usually unreliable before
the 16th week, and by the time results are known, pregnancies are
well into their middle third, when {*filter*}s are more complex and
risky. // In both methods, laboratory workers analyze the
gene-carrying chromosomes in the nuclei of removed cells for many
types of genetic errors, including those that cause such
inherited diseases as sickle cell anemia, Down's syndrome and Tay
Sachs disease." --- Charles Petit, San Francisco Chronicle, 9
March 1989
"Just four letters can answer age-old questions about the causes
of disease. Strings of G, C, A and T -- the nucleic acid bases
guanine, cytosine, adenine and thymine -- spell out genes that
instruct cells to perform critical functions. Or not. The
simple switch of a T for an A causes sickle cell anemia, for
instance. Recently the severity of several major cancers has
been linked to changes in a gene called p53. // The process of
linking genetic variations to disease is being vastly simplified
by machines. Much work on improving the equipment is being done
with government funding under the auspices of the international
Human Genome Project." --- Deborah Erickson, "Diagnosis by DNA",
Scientific American 267(4):116, October 1992
- Larry
Sickle Cell Anemia