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Essay Name       : 801.txt 
Uploader         : -
Email Address    : -
Language         : English
Subject          : Biology
Title            : The Thread of Life: DNA
Grade            : 90%
School System    : High School
Country          : USA
Author Comments  : Not very long, but OK paper
Teacher Comments : Don't remember
Date             : 10/16/95
Site found at    : friend
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	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? 
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