Why is DNA heated to 95°C in the polymerase chain reaction?

• A. To separate the two strands of the DNA by breaking hydrogen bonds
• B. To inactivate the polymerase enzyme
• C. To anneal primers to the template
• D. To synthesize new DNA strands

Answer: (A)

DNA is heated to 95°C to disrupt the hydrogen bonds that hold the two strands together, denaturing the double helix into single strands. This denaturation creates single-stranded templates so the primers can bind in the next step. The high temperature specifically breaks those base-pair interactions without permanently destroying the DNA, and the process uses a thermostable polymerase that remains active during the subsequent, cooler step where primers anneal and DNA synthesis occurs.