tohave a photograph taken of the catheter lying in his
right auricle. He abandoned cardiology after being
ridiculed for this act. André F. Cournand and Dickin-
son W. Richards perfected this procedure. He was
appointed chief of the surgical clinic of the city hospital
at Dresden-Friedrichstadt and at the Robert Koch Hos-
pital, Berlin. During World War II he became a prisoner
of war until his release in 1945, when he went into
practice with his wife. Beginning in 1950 he practiced
as a urological specialist at Bad Kreuznach. In 1958 he
was chief of the surgical division of the Evangelical
Hospital at Düsseldorf until 1970.
In 1956 he was awarded, together with André COUR-
NANDand Dickinson W. RICHARDS, the Nobel Prize in
physiology or medicine for their work in development of
cardiac catheterization. He was also appointed honorary
professor of surgery and urology at the Johannes Guten-
berg University, Mainz. He was awarded many honors
and belonged to a number of scientific organizations dur-
ing his career. He died on June 1, 1979, in Schopfheim, in
the Black Forest in West Germany.
fossil Preserved remains or imprints of once-living
plants or animals or their tracks, or burrows, or prod-
ucts (e.g., dung).
founder effect When a small population migrates
from a larger population, becomes isolated, and forms
a new population, the genetic constitution of the new
population is that of a few of the pioneers, not the
main population source; the genetic drift observed in a
population founded by a small nonrepresentative sam-
ple of a larger population; it is the difference between
the gene pool of a population as a whole and that of a
newly isolated population of the same species.
See alsoGENETIC DRIFT.
fragile X syndrome It is the most common form of
genetically inherited mental retardation. Named for its
association with a malformed X chromosome tip, the
frequency of the syndrome is greater in males than in
females, occurring in approximately 1 in 1,000 male
births and 1 in 2,500 female births. In 1991 the
causative gene FMR-1 (fragile X mental retardation)
was discovered. Fragile X is the most common inherit-
edcause of learning disability and affects boys and girls
of all ethnic groups.fragmentation A mechanism of asexual reproduc-
tion in which the parent plant or animal separates into
parts that re-form whole organisms.frameshift mutation A mutation via an addition of
a pair or pairs of nucleotides that changes the codon
reading frame of mRNA by inserting or deleting
nucleotides.fraternal In offspring, twins that are not identical.
Identical twins occur when both fetuses come from
the division of a single fertilized egg and have separate
placentas. Fraternal twins can be either same or oppo-
site sex.free energy Energy readily available for producing
change in a system.free radical A molecule that contains at least one
unpaired electron; highly reactive chemical that usually
exists only for a short time. Formed in the body during
oxidation, a normal by-product of metabolism, they
can bind with electrons from other molecules and can
cause cellular damage by disrupting normal cellular
processes, but can be kept in check by antioxidants
such as certain enzymes or vitamins (C and E).freshwater The Earth is mostly water, which covers
74 percent of its surface. Freshwater accounts for only
3 percent of the total water. Freshwater is water that
contains less than 1,000 milligrams per liter (mg/L) of
dissolved solids. The United States Geological Survey
(USGS) states that, generally, more than 500 mg/L of
dissolved solids is undesirable for drinking and many
industrial uses.Fritts, Harold Clark(1928– ) American Botanist,
Dendrochronologist Harold Fritts was born on134 fossil