Polymerase chain reaction (PCR) is a technique used to amplify (copy) DNA. Suppose a single, linear molecule of double‑stranded DNA (dsDNA) is amplified by PCR. After one PCR cycle, how many molecules of dsDNA will there be?

There will be 2 molecules.

Explanation:

Each PCR cycle replicates one DNA molecule. This cycle lasts about 2 minutes where the Denaturation (where the DNA double helix is separated) phases occur, Bonding (where prmiets begin to establish complementary hydrogen bonds to the nitrogenous bases of the two DNA strands) and Synthesis (Where DNA polymerase begins to create new strands of DNA). Prior to the first round of PCR there was a DNA sample. However, after one cycle this sample was replicated, so the PCR reaction will follow with 2 DNA samples.