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Unformatted text preview: 1 Spring '10 "MODEL BUILDING: DNA ON A GRAND SCALE" POST-LAB ASSIGNMENT Note: Pages 3 & 4 of this document contain the questions for your post-lab assignment. Download these pages, fill in your answers to the questions, and turn them in to your TA at the beginning of the next lab, "Exploring Bioinformatics." Questions 2, 3, & 4 of the assignment ask you to apply your understanding of the structure and function of the DNA molecule to the technique of PCR, as explained on pages 1 & 2 below. Answer these questions using this background information and your experience working with models of DNA in lab. About the polymerase chain reaction, PCR One of the most valuable techniques in molecular biology and genetic engineering is the polymerase chain reaction , PCR . Developed in 1983 by Kary Mullis (who as a result won the Nobel Prize), it allows fragments of DNA to be quickly and accurately copied many times over. The procedure has found wide application in copying DNA to sequence genomes, recover genes from extinct animals, diagnose genetic disorders, detect viral infections like HIV, and analyze biological evidence in criminal investigations. Although PCR can be used with tiny quantities of DNA, the investigator must first know something about the stretch of DNA that is to be amplified, specifically the sequence of bases flanking either side of the it. This information is used to make primers-- short stretches of single-stranded DNA -- that are necessary to initiate replication by DNA polymerase. The primers are added to the sample of DNA along with a supply of nucleotides (activated by having three phosphate groups attached to their sugars so they can chemically bond in a chain) along with DNA polymerase to catalyze the bonding of the nucleotide chain. Starting with an ample supply of these reagents present with the DNA sample, the PCR process has three steps: 1) Heating to denature (melt) the double-stranded DNA sample to separate the strands of the double helix and make single-stranded DNA....
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