Methods for Analyzing DNA: A source of heat-stable DNA polymerase commonly used in PCR is which of the following organisms?

• A. Saccharomyces cerevisiae
• B. Homo sapiens
• C. Thermus aquaticus
• D. Escherichia coli

Answer: (C)

Verified step by step guidance

1. Understand the context of the question: PCR (Polymerase Chain Reaction) requires a DNA polymerase enzyme that can withstand high temperatures used during the denaturation step.
2. Recall that most DNA polymerases from common organisms like Saccharomyces cerevisiae (yeast), Homo sapiens (humans), and Escherichia coli are not heat-stable and would denature at the high temperatures used in PCR.
3. Identify that Thermus aquaticus is a thermophilic bacterium, meaning it thrives at high temperatures, and its DNA polymerase enzyme is naturally heat-stable.
4. Recognize that the heat-stable DNA polymerase from Thermus aquaticus, commonly called Taq polymerase, is widely used in PCR because it remains active after repeated heating cycles.
5. Conclude that the source of heat-stable DNA polymerase used in PCR is Thermus aquaticus, making it the correct answer among the options provided.