PCR and Gel Electrophoresis Questions and Answers Graded A+

PCR and Gel Electrophoresis Questions and Answers Graded A+ What’s the primary purpose of PCR before running a gel electrophoresis? PCR amplifies specific DNA segments, making millions of copies so that there’s enough to see when you run it through the gel. How does PCR know which part of the DNA to copy? PCR uses primers—short sequences that match the start and end of the target DNA region, telling the enzyme exactly where to begin and stop copying. What role does the polymerase enzyme play in PCR? The polymerase acts like a DNA-building machine, copying the DNA strand by adding nucleotides one at a time during each cycle. Why do you run a PCR product through gel electrophoresis? Gel electrophoresis separates the amplified PCR products by size, allowing you to confirm if the correct DNA fragment was copied. 2 What are the three main steps in PCR, and why do they repeat? The three steps are denaturation (separating the DNA strands), annealing (binding the primers), and extension (copying the DNA). They repeat to exponentially amplify the DNA with each cycle. How do you know your PCR worked after running the gel? If PCR worked, you’ll see clear bands at the expected size on the gel, indicating that the DNA was successfully amplified. What could cause no bands to appear on your gel after PCR? No bands could mean that PCR didn’t amplify anything, possibly due to faulty primers, missing reagents, or incorrect cycling conditions. Why is Taq polymerase special for PCR? Taq polymerase is heat-resistant, allowing it to survive the high temperatures of PCR denaturation and continue copying DNA during each cycle. What’s the purpose of the thermal cycler in PCR? 3 The thermal cycler quickly heats and cools the sample, controlling the temperature shifts required for denaturation, annealing,