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