DNA replication. Animation of a sample of DNA (deoxyribonucleic acid) being placed in a thermocycler where it will be replicated by repeated heating and cooling (thermocycling) in the presence of the enzyme DNA polymerase. The animation shows the process occurring at the molecular level. The enzyme (blue) travels along a DNA strand matching complementary nucleotides. This annealing occurs at a temperature of 55 degrees Celsius. The thermocycling (heating to 95 degrees Celsius for denaturing) breaks open the strands for further replication, and repeated cycles of this (with an intermediate temperature of 72 degrees Celsius for elongation) amplifies the DNA into a quantity which can be used for analysis.