To denature DNA, what temperature should a thermocycler reach?

The correct answer is to reach a temperature between 94-98°C for the denaturation of DNA. This high temperature is essential because it provides the energy needed to break the hydrogen bonds that hold the two strands of the DNA double helix together. As the temperature exceeds 90°C, the double-stranded DNA separates into single strands, making it accessible for subsequent processes such as primer annealing and DNA synthesis.

This denaturation step is crucial in techniques like polymerase chain reaction (PCR), where precise separation of DNA strands is required for successful amplification. Lower temperatures, such as those listed in the other choices, would not be sufficient to effectively denature the DNA, as they would not provide enough thermal energy to disrupt these strong hydrogen bonds adequately. Thus, the high temperature range of 94-98°C is specifically chosen to achieve complete denaturation.