The "thread of life", is deoxyribonucleic acid, otherwise known as DNA. It is the spiral
shaped molecule found in the nucleus of cells. Scientists have known since 1952 that DNA
is the basic substance of heredity. This was hypothesized, and later confirmed by James
D. Watson and Francis Crick. They also know that it acts like a biological computer
program over 3 billion bits long that "spells" out instructions for making the basic
building blocks of life.
DNA carries the bodies genetic code, controls the development of an embryo, is capable of
duplicating itself, and is able to repair damage to itself. DNA can be manipulated to
change all kinds of things.
All DNA molecules consist of a linked series of unites called nucleotides. Each DNA
nucleotide is composed of 3 subunits: a 5 carbon sugar called deoxyribose, a phosphate
group that is joined to one end of the sugar molecule, and one of several different
nitrogenous bases linked to the opposite end of the deoxyribose. There are 4 nitrogen
bases called adenine, guanine, thymine, and cytosine. In DNA adenine pairs with thymine
and guanine with cytosine.
Medicine's ability to diagnose continues to exceed its ability to treat or cure. For
example, Huntington's Chorea is an inherited disease that develops between the ages of 30
and 45, can be diagnosed before any symptoms appear. This can be hard for both the
individuals with the disease and their family.
There is a 3 billion dollar project underway right now called the Human Genome Project,
a 15 year program to make a detailed map of every single gene in human DNA. With
automated cloning equipment to steer scientists through the DNA, scientists are finding
human genes at the rate of more than one a day. This may not sound like very much but as
technology increases the rate at finding them will increase. Since January 1993 to
January 1994 scientists have located the genes for Huntington's disease, Lou Gehrig's
disease, and the "bubble-boy" disease. Scientists are expected to find the first breast
cancer gene any week now.
Even with the best tools of today, the progress is full of surprises. Human DNA is not
like that of plants, in which the trait of color of a flower is determined by one gene.
Even the color of a human eye can involve the interaction of several genes. Some complex
genes, such as cystic fibrosis, can go wrong in any number of places. Scientists have
already accounted for 350 places where the cystic fibrosis gene mutates, and more are
being uncovered weekly.
Many environmental factors, some physical, other's chemical, can alter the structure of
a DNA molecule. A mutation occurs when such alterations lead to a permanent change in
the base sequence of a DNA molecule. Mutations result in an inherited change in a
protein synthesis. DNA is damaged by exposure to ultraviolet (UV) light. The DNA does
have the ability to repair it self, however.
DNA can also be used to match suspects in a crime. Each person's DNA is different from
everyone else, except in the case of identical twins in which it is identical. By
comparing substances left at a crime scene (blood or semen samples) law enforcement
agencies are able to match the DNA at the crime scene with a certain suspect. A recent
example of this is the O.J. Simpson case, in which the lawyers are trying to match up
O.J.'s DNA with the DNA in the blood found at the crime scene.
Many questions have been raised by a number of people and scientists about the ethics of
DNA research. It was once feared that the insertion of a disease causing substance could
cause a deadly epidemic in the general population upon accidental release. But, since
1973 when they first used the technique it has been transferred thousands of times
without any of the feared catastrophes occurring. But, still there are many questions
remaining to be answered. Is it right for people to change their babies' eye color, or
any other aspect of their baby? Should employers be allowed to see your DNA, to see if
you are at risk for a certain disease?
|