Question

What makes the Taq DNA polymerase frequently used for a polymerase chain reaction (PCR) different from other DNA polymerases, and why is it preferable?

Short answer

Answer: Taq DNA polymerase is preferred for PCR due to its thermostability and high processivity. It can function at high temperatures required for PCR and synthesize long stretches of DNA efficiently. While its error rate is higher than other polymerases, it can be managed through proper experimental design and is not a major issue for PCR applications. These properties make Taq DNA polymerase more suitable for PCR compared to other DNA polymerases.

Step-by-step solution

Introduce Taq DNA polymerase

Taq DNA polymerase is an enzyme derived from the thermophilic bacterium Thermus aquaticus. This enzyme is unique as it is able to synthesize DNA at high temperatures. PCR is a technique that relies on repeated cycles of temperature changes for DNA denaturation, primer annealing, and DNA synthesis, thus making enzymes that work at high temperatures preferable.

Describe thermostability of Taq DNA polymerase

One of the primary differences between Taq DNA polymerase and other DNA polymerases is thermostability. Taq DNA polymerase can withstand the high temperatures required for PCR, typically ranging between 72°C and 94°C, without losing its enzymatic activity. Many other DNA polymerases would denature, or become inactive, under these conditions.

Explain the processivity of Taq DNA polymerase

Taq DNA polymerase has a high processivity, which means it can synthesize a long stretch of DNA without dissociating from the template. This allows the enzyme to efficiently replicate DNA during the PCR process, speeding up the overall reaction and reducing the likelihood of incomplete DNA synthesis.

Describe the error rate of Taq DNA polymerase

Taq DNA polymerase has a higher error rate than many other DNA polymerases. While this may seem like a disadvantage, it is usually not an issue for most PCR applications, as the primary goal of PCR is to amplify DNA rather than ensuring its complete fidelity. The relatively low fidelity of Taq DNA polymerase can be accounted for by using appropriate controls and experimental design.

Summarize the reasons for preferring Taq DNA polymerase for PCR

In summary, Taq DNA polymerase is frequently used for PCR due to its thermostability, allowing it to function at high temperatures required for the denaturation, annealing, and elongation steps of PCR. Additionally, its high processivity makes it an efficient enzyme for quickly synthesizing large amounts of DNA. While Taq DNA polymerase does have a higher error rate than other polymerases, this can be managed through proper experimental design and is usually not a major issue for PCR applications. These properties make Taq DNA polymerase preferable for PCR compared to other DNA polymerases.