PCR  Polymerase Chain Reaction  Used controlled temperatures and enzyme taq polymerase to replicate pieces of DNA PCR Allows scientists to make many copies from a few target DNA molecules  Taq polymerase is the DNA replication enzyme found in bacteria that live in hydropylilic vents in the ocean  PCR  Thermus aquaticus  These bacteria work at very high temperatures  Temperature is used to control PCR reactions PCR  Three step process  Performed in a machine called a thermocycler  Machine alters temperature at each step of process PCR  Process times is repeated many PCR Process  Separation 95 degrees C  Annhealing – cool to 35-58 C for primers to bind to complimentary DNA regions PCR Process  Extension – warm to 72 C for Taq polymerase to build a new DNA strand from primed regions PCR  1st cycle= 2 copies th  20 cycle= 1,048,576 copies Gel Electrophoresis  Process of using an electrical field in agar to separate DNA and RNA based upon size Electrophoresis  First used with RNA  Provides a sequence of DNA fragments  Samples of DNA are loaded into a gel matrix Electrophoresis  Electric current is applied  Molecular fragments separate as they are pushed through the gel Electrophoresis  Fluorescent dye is used to stain the DNA fragments  Electrodes at each end of the gel create the current across the gel Electrophoresis  Since DNA is negatively charged, it travels from the negative electrode toward the positive electrode Electrophoresis Heavier or larger DNA fragments move more slowly than smaller ones  Smaller fragments will travel farther across the gel during the run  DNA Profiling  Identifying an organism based on regions of DNA that vary greatly from one organism to another DNA Profiling  Used most widely today in identifying people who cannot identify themselves  Murder victims DNA Profiling  Known as DNA fingerprinting  No 2 individuals have identical DNA sequences except identical twins DNA Profiling  Makes it possible to identify nearly every person on earth.