In the past, at least 1μg of DNA was required for DNA profiling. With PCR, only tiny amounts of DNA are needed as DNA can be replicated from very small amounts.Amplification is achieved first by denaturing the DNA i.e. separating the strands at 95°C into single-stranded DNA by breaking the hydrogen bonds. DNA primers are then added to the ends at 50-65°C. The primers anneal to the ends of the single-stranded DNA. Nucleotides are added and the temperature is raised to 72-75°C for about a minute so the Taq DNA polymerase can add nucleotides to the primer. The DNA polymerase used comes from Thermus aquaticus, a bacterium found in hot springs. The Taq DNA polymerase has an optimum temperature of about 72°C.