Question

DNA fragments must be denatured during the polymerase chain reaction due to which of the following?

A) To maintain the stability of the DNA structure.
B) To facilitate the separation of DNA strands.
C) To prevent the formation of new DNA fragments.
D) To preserve the original DNA fingerprint.

Answer 1

DNA fragments are denatured in PCR to separate the double-stranded DNA into single strands, allowing primers to anneal and DNA polymerase to synthesize new DNA strands.

Step-by-step explanation:

DNA fragments must be denatured during the polymerase chain reaction (PCR) to facilitate the separation of DNA strands. Denaturing involves heating DNA to break the hydrogen bonds holding together the two strands, which converts the double-stranded DNA into two single strands. This is crucial for the subsequent steps of PCR, including annealing, where primers that are complementary to the DNA sequence can attach to each single strand and serve as starting points for DNA synthesis, and extension, where the DNA polymerase synthesizes new DNA strands complementary to the original strands.

The PCR process is performed over multiple cycles, with each cycle consisting of three key steps: denaturation, annealing, and extension. High temperatures are used during the denaturation phase to physically separate the two strands of the DNA molecule. As PCR involves repeated cycles of heating and cooling, the DNA polymerase used must be heat-stable to withstand those high temperatures, such as the Taq DNA polymerase from the thermophilic bacterium Thermus aquaticus.