Question

\(Taq\) polymerase is used for PCR because it ____________. a. tolerates the high temperature needed to separate DNA strands b. is an enzyme from a bacterium c. does not require primers d. is genetically modified

Short answer

The correct answer is a: Taq polymerase tolerates the high temperature needed to separate DNA strands.

Step-by-step solution

Understand PCR Process

Polymerase Chain Reaction (PCR) is a technique used to amplify small segments of DNA. This process involves cycles of heating and cooling to separate DNA strands and then synthesizing new strands using a DNA polymerase.

Identify Role of Taq Polymerase

Taq polymerase is a heat-resistant DNA polymerase originally isolated from the thermophilic bacterium Thermus aquaticus. Its main characteristic is its ability to withstand the high temperatures (around 95°C) used during the denaturation step of PCR, where DNA strands separate.

Analyze Answer Choices

Evaluate each answer choice in relation to the role of Taq polymerase in the PCR process: - a. Tolerates the high temperature needed to separate DNA strands: This is accurate because Taq polymerase is functional at high temperatures, which are necessary during DNA denaturation. - b. Is an enzyme from a bacterium: While true, this doesn't address why Taq polymerase is used in PCR specifically. - c. Does not require primers: This is incorrect as Taq polymerase does require primers to begin DNA synthesis. - d. Is genetically modified: This is misleading in this context as Taq is naturally heat-resistant.

Select the Correct Answer

Given that Taq polymerase's heat tolerance is critical to its function in PCR, the correct answer is: a. It tolerates the high temperature needed to separate DNA strands.

Key concepts

Taq polymerase

Taq polymerase is an essential enzyme in the world of molecular biology, specifically used in the polymerase chain reaction (PCR) process. This remarkable enzyme was originally isolated from the bacterium known as Thermus aquaticus.
What makes Taq polymerase special is its heat resistance. Unlike most enzymes that would denature at high temperatures, Taq polymerase can withstand and function at temperatures around 72°C, making it ideal for PCR experimentation.
This enzyme's ability to tolerate heat is critical during the PCR process where the temperature fluctuates dramatically. It allows scientists to efficiently and effectively amplify tiny segments of DNA.

DNA denaturation

DNA denaturation is a crucial step in the PCR process. It involves heating the DNA to around 95°C, causing the two strands to separate. This is necessary to expose the DNA strands for copying.
Without denaturation, the enzyme cannot access the DNA sequence to start the replication process.
Think of it like unzipping a zipper to lay the fabric flat. When the strands separate, they present single strands that Taq polymerase can use to synthesize new DNA strands.

• It exposes the nucleotide sequences for replication.
• High temperatures ensure separation of the strands.

Denaturation prepares the DNA for the subsequent steps of PCR by making it accessible for the action of Taq polymerase.

Thermophilic bacterium

A thermophilic bacterium like Thermus aquaticus is able to survive in extremely hot environments. These bacteria thrive at high temperatures, typically found in hot springs or hydrothermal vents.
Thermophilic organisms produce enzymes that are thermostable like Taq polymerase.
This property makes thermophilic bacteria invaluable for industrial and scientific applications. The ability of their enzymes to remain functional at high temperatures is harnessed in processes like PCR, where heat stability is a necessity.
These bacteria are studied not only for their utility but also for understanding life in extreme conditions.

DNA synthesis

DNA synthesis during PCR replicates the DNA, producing multiple copies of a specific DNA segment. Taq polymerase plays a vital role in this phase by "reading" one strand of DNA and synthesizing a new, complementary strand.
This replication occurs in cycles, with each cycle ideally doubling the amount of DNA.

• The presence of primers is crucial to guide Taq polymerase where to start synthesizing.
• 95°C for denaturation, 72°C for synthesis.

During the elongation phase, Taq polymerase adds nucleotides to the growing DNA strand, extending it piece by piece. DNA synthesis is fundamental to PCR, ensuring that ample copies of DNA are available for analysis.

DNA amplification

DNA amplification is the principal goal of PCR; it allows a small amount of DNA to be copied exponentially to generate millions or even billions of copies of a target DNA sequence.
The PCR process involves repeated cycles, each consisting of denaturation, annealing, and extension, which cumulatively amplify the DNA.
Through this method, a tiny sample can be transformed into a substantial amount, making it easier to perform further analyses that require larger quantities of DNA.
This process has revolutionized fields such as genetic fingerprinting, cloning, medical diagnostics, and more, highlighting the importance of DNA amplification techniques in modern science.