DNA Structure
The "Thread of Life", is deoxyribonucleic acid, also known as DNA.
This
molecule which is the bases of life, is spiral shaped and found in the
nucleus
of cells. DNA has the genetic code for bodies, controls development
of
embryo’s, and is able to repair damage caused to itself. All DNA
molecules
have linked units called nucleotides. These nucleotides have
sub-units that have
5 carbon sugars that are called deoxyribose. DNA is
composed of four bases
called adenine, thymine, guanine, and cytosine. These
are some of the main
principles of DNA. What we know today about structure of
DNA begins in 1868 when
a Swiss biologist Friedrich Miescher did the first
experiments on the nuclei of
cells. Miescher used the nuclei of pus cells
from old medical bandages. In these
pus cells he found What We know today
about structure of DNA begins in 1868 when
a Swiss biologist Friedrich
Miescher did the first experiments on the nuclei of
cells. Miescher used the
nuclei of pus cells from old medical bandages. In these
pus cells he found
phosphorus with a substance he called nuclein. This nuclein
has an acidic
portion which is classified as DNA. Another scientist Thomas Hunt
Morgan
made an important discovery around 1900. He observed that
certain
characteristics were inherited quickly through numerous generations
of fruit
flies. So he made the conclusion that these genes must be near one
another on
the chromosome. In 1943 Oswald Avery, Colin MacLeod, and Maclyn
McCarty, three
scientists working in the Rockefeller institute, preformed an
experiment by
taking DNA from a virulent (disease-causing) strain of
Streptococcus pneumonae
and transformed a non-virulent (inactive) form back
to a virulent form. Avery,
MacLeod, and McCarty discovered from their
experiments that DNA carried a
virulent message that can be transferred into
the recipient of non-virulent
cells. This proved that DNA was a carrier of
genetic information. An important
discovery of the 1940’s was the discovery
by Erwin Chargaff who established
that "heredity’s alphabet" which are the
four bases adenine (A), guanine
(G), thymine (T), and cytosine(C) can occur
in different orders in different
organisms. In 1953 James Watson and Francis
Crick put forth a radical new idea
about DNA. Their idea suggested that the
DNA molecule was made up of two helical
chains instead of three intertwined
chains as previously thought. Today we have
a strong knowledge of DNA and
scientists are applying that knowledge to a three
billion dollar project
called the human genome project. This project will
examine the structure of
human DNA and map out every single gene in the human
body and will take 15
years. The strong knowledge that we have of DNA allows the
scientist to map
out the genes at about 1 to 2 per day. This may not seem to be
a very fast
rate but scientists have already found the genes that cause diseases
such as
Hunnington’s, Lou Gerhig’s, and the "Bubble-Boy" disease.
Another way
that we use our strong knowledge of DNA is in criminal
identification. This
plays a major role in today’s society. Because each
person’s DNA is different
(except in identical twins) police officers can take
blood or semen samples
from a crime scene and take them to the lab for
identification. This can
insure the guilt or innocence of a suspect. An example
of this is the O.J.
Simpson case where investigators tried to match O.J.’s DNA
to the DNA at the
scene of the crime. Another way scientists apply their
knowledge of DNA today
is by using special enzymes called restriction enzymes
that cut through the
phosphate of DNA and these cut ends are called "sticky
ends" because they
easily attract other tails from other DNA. Scientist use
these restriction
enzymes for genetic engineering by removing a gene from one
organism to
another. In the future DNA has great possibilities for the
betterment of
mankind and also the detriment. The most obvious and
controversial
possibility would be the cloning of humans. Scientists have
already cloned sheep
and other such organisms but have yet to take the step
for cloning a human even
though the technology is in place, the ethics of
this may not be. The method to
arrive at is quite simple. The embryo of an
organism is removed in the early
development stage from the uterus then split
and each separate part is placed in
a surrogate uterus. Scientist are trying
to clone organisms beyond the early
embryonic stages, making for a much more
difficult challenge. In 1996 Scottish
scientists were able to clone a sheep,
Dolly, by taking skin cells of a donor
sheep and were deprived of nutrients
to halt cell production. Then an
unfertilized egg is taken from another sheep
with its nucleus removed, to erase
any genetic information and then finally
fused with the skin cells from the
first donor sheep. Though Dolly
characteristics are the same as the sheep that
the skin cells were taken
from, she is not a 100% clone. She is not a true clone
because not all
organisms are found in the nucleus and therefore still retain
some of the
traits from the surrogate sheep. The human Genome Project that is
said to be
done by 2005 will sequence more 35 million pairs of human DNA.
Because of
such advanced technologies in the future and continually growing
knowledge of
DNA we may be able to find cures for such diseases as cancer or
AIDS or
even deformities such as sickle cell anemia or down syndrome. DNA
technology
is one of the leading sciences going into the 21st century. Because
it could
potentially cure or eliminate such diseases or deformities as AIDS or
down
syndrome it could also potentially harm us in the future with more
lethal
biological weapons. However anything dealing with DNA is a highly
complicated
and sensitive issue to most people. This knowledge is so powerful
that we are
able to play God, in a sense, and create or alter any organism we
choose. That
is why I believe that for the betterment of mankind we must
regulate and
restrict this information to insure that it is used for ethical
purposes of
mankind.