Designing good primers involves understanding some other concepts of DNA synthesis:
• the melting temperature of the double-stranded DNA (to know what annealing temperature to use for your PCR)
• the stability and relative GC content (GC bonds are more stable than AT bonds, which affects the melting temperature)
• avoiding complementarity within the primer sequence, as this inhibits proper annealing
But there are a number of software programs to help you design your primers, many of which are freely available on the internet (see Resources at the end of this section). Primers can be purchased from any DNA synthesis facility.