Hexamer primers are sequences composed of six random nucleotides. For MDA applications, these primers are usually thiophosphate-modified at their 3’ end to convey resistance to the 3’&ndash;5’ exonuclease activity of Ф29 DNA polymerase. MDA reactions start with the annealing of such primers to the DNA template followed by polymerase-mediated chain elongation. Increasing numbers of primer annealing events happen along the amplification reaction.