1. PCR Polymerase Chain Reaction

2. What is it and how is it useful?  A quick, easy method for amplifying (creating billions of copies) of unimaginably tiny amounts of DNA  Methodology closely related to process of DNA replication  Used in forensic science to analyze small quantities of DNA recovered from a crime scene such as: - saliva on a cigarette butt or envelope - saliva on a cigarette butt or envelope - DNA in the root of a single strand of hair - tissue under the fingernails of a victim - DNA in a single drop of blood - a small semen stain

3.  Used to detect disease/infection in an organism and treat it before a condition worsens  Anthropology/archeology – PCR has allowed tiny fragments of DNA that have been exposed and degraded over thousands of years to be amplified and studied

4. How does PCR work? Need: The DNA molecule you want to copy ( the template) 2 DNA primer molecules – short, single stranded chains of nucleotides that attach to the “unzipped DNA” DNA polymerase A system for heating and cooling the DNA strands

5. The Steps….. 1. DNA molecule separated by heating the sample to 90-96 °C 1. DNA molecule separated by heating the sample to 90-96 °C 2. Strands are cooled so that DNA primers can be added. Primers bind to complementary bases on the two separated strands of DNA. 2. Strands are cooled so that DNA primers can be added. Primers bind to complementary bases on the two separated strands of DNA. 3. A special DNA polymerase (Taq polymerase) reads the template strand and matches it with complementary nucleotides found within the DNA suspension (test tube) 3. A special DNA polymerase (Taq polymerase) reads the template strand and matches it with complementary nucleotides found within the DNA suspension (test tube)

6. Note: Taq polymerase comes from Thermus aquaticus – a type of bacteria that lives in hot springs END RESULT – 2 new helixes each made up of one of the original strands plus a newly assembled complementary strand Each subsequent cycle doubles the # DNA molecules copied – exponential increase Ex: 30 cycles – 2 30 DNA copied Each cycle takes 1-3 minutes. Therefore, in 1 hour you can have over a billion strands of a specific DNA molecule