FREE ESSAY ON STRUCTURE OF DNA

STRUCTURE OF DNA

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.