DNA is the "master molecule of life". Every living creature, from amoebas to zebras, carries with it the coded messages of heredity, which govern everything from eye color to allergies. Its discovery, solved by James Watson and Francis Crick 41 years ago, led to one scientific triumph after another. Shelley and I explored these findings and introduced the class to the most applicable use of DNA in today's society: DNA and its service in the sensational field of criminal investigation. Therefore, our goal was to first explain the structure of DNA, the two analytical methods used to examine DNA, the controversies that might arise using these methods, and finally their impact on the field of forensic medicine. In the following informative text I will explain the first aspect of DNA and give an in-depth explanation of its scientific structure and the means used to analyze this "master molecule of life". Inside the cell's nucleus is a ribbon of the enormous DNA molecule, deoxyribonucleic acid, spread across 23 chromosomes. Only a few microns wide, it would stretch a full six feet if unrolled. It is made up of 2 matched strands twisted into a spiral called a "double helix". Each strand contains about 3 billion repeating chemical units called nucleotides, each incorporating one of four different types of chemical bases: adenine, cytosine, guanine, and thymine. The DNA of the two strands is complementary and as such only guanine binds to cytosine and adenine to thymine. Hidden among these sequences and representing only 2% of human DNA are the gene sequences that code for the production of proteins on which all life depends. It is estimated that humans have 50,000 to 100,000 genes, each composed of 1,000 to approximately 2 million nucleotides and their corresponding bases. This large number afforded by the arrangement of these four bases reveals the secret of the genetic code's vast information-carrying capacity. The rest of the human genome, about 98%, is non-coding "junk" DNA. Only 8 years ago DNA was introduced into the field of criminal investigations. Previously, it had been used as a means of identifying genes for inherited diseases such as Huntington's disease and cystic fibrosis. It was initially established to be used in paternity and immigration cases; however, it was later used in 1986 as reliable and substantial evidence to convict Colin Pitchfork of murder..