Question

the polymerase chain reaction (pcr) is a laboratory technique used to make millions or billions of copies of certain dna segments using only dntps, rna primers, mg²⁺, and a dna polymerase from thermus aquaticus, a bacterium that lives at high temperatures. the pcr consists of three steps, repeated 25 - 35 times. the first is denaturation, where the solution is heated to 94 - 98°c to separate the template dna strands. the second is annealing, where the solution is cooled to 50 - 65°c to allow the primers to bind to the dna. the third is extension/elongation, where the solution is heated to 75 - 80°c to allow dna polymerase to synthesize the complementary dna strands. nicolaus has dna samples with varying g - c content: sample a (30% g - c), sample b (50% g - c), and sample c (70% g - c). during the pcr, he notices that different denaturation temperatures are required for proper amplification of each sample. if he uses the denaturation temperature of sample a on samples b and c, what would be the most likely outcome?

all the samples would amplify equally well
sample a would over - amplify while sample c would under - amplify
sample c would fail to denature properly and show poor amplification
sample a would show the worst amplification results
only sample b would amplify successfully

Explanation:

G - C base - pairs have three hydrogen bonds compared to two in A - T base - pairs. Samples with higher G - C content require higher denaturation temperatures. Sample C has the highest G - C content (70%). Using the lower denaturation temperature of sample A (30% G - C) on sample C will likely prevent proper denaturation of sample C's DNA strands, resulting in poor amplification.

Answer:

Sample C would fail to denature properly and show poor amplification