UNDERSTANDING DNA

Historical Information 1953—James Watson and Francis Crick discover the configuration of the DNA molecule 1980—Ray White describes first polymorphic RFLP marker 1985—Alec Jeffreys isolates DNA markers and calls them DNA fingerprints 1985—Kary Mullis develops PCR testing 1988—FBI starts DNA casework 1991—first STR paper 1998—FBI launches CODIS database

Introduction Portions of the DNA structure are as unique to each individual as fingerprints. The gene is the fundamental unit of heredity. Each gene is actually composed of DNA specifically designed to carry the task of controlling the genetic traits of our cells.

Introduction Deoxyribose sugar Phosphate Nitrogenous Base

The Bases Four types of bases are associated with the DNA structure: adenine (A), guanine (G), cytosine (C), thymine (T).

The Bases The bases on each strand are properly aligned in a double-helix configuration, which is two strands of DNA coiled together. As a result, adenine pairs with thymine and guanine pairs with cytosine. This concept is known as base pairing. The order of the bases is what distinguishes different DNA strands.

DNA at Work DNA directs the production of proteins, which are made by combining amino acids. The sequence of amino acids in a protein chain determines the shape and function of the protein. Each group of three nucleotides in a DNA sequence codes for a particular amino acid. – Example: G-A-G codes for the amino acid glutamine, while C-G-T codes for alanine.

General DNA Information Double helix—two coiled DNA strands Composed of nucleotides—units containing a sugar molecule (deoxyribose), a phosphate group, and a nitrogen-containing base In humans, the order of these bases is 99.9 percent the same. Four bases: Adenine Cytosine Guanine Thymine Bases always pair A to T and G to C.

 Esterase-D (esD)  PGM  pepA  Enzymes catalyze  Each enzyme has a responsibility: to convert one sugar group to another 3 ENZYMES IN DNA

Where Is DNA Found? Genes are portions of DNA that code for specific proteins. DNA is found in all nucleated body cells—white blood cells, semen, saliva, urine, hair roots, teeth, bone, tissue. Most abundant in buccal (cheek) cells Red blood cells have no nuclei, and therefore, no nuclear DNA. DNA obtained from blood comes from white blood cells.