Before sequencing, these PETs are ligated to adaptors to which PCR primers anneal for amplification. The 8 variable nucleotides anneal randomly to the single stranded genomic DNA molecule. The temperature at which the primers anneal is critical. The amplification reaction initiates when multiple primer hexamers anneal to the template. Then the repeats anneal and the resulting molecule is repaired using polymerase and ligase. Rapid thermal anneal (RTA) is a subset of Rapid Thermal Processing. After a short timestep it is degraded, the overlaps can anneal and be ligated. As a result, a vacuum anneal is needed to convert the oligomers to high polymer. Proteins such as RAD52 can help DNA anneal. The newly synthesised strands anneal to one another, but mismatches are common. The final stage is to anneal the finished glass to avoid damage from shrinkage stresses. These short fragments and the templates anneal together based on sequence complementarity. After the strands anneal, a small flap of DNA can sometimes remain. The DNA has a dumbbell-like structure as the ends fold in and self anneal. In many cases, initialisation is accomplished by letting the system anneal to the ground state.