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In genetic engineering, Primer is an oligonucleotide with 18-26 base pair (bp) that attached to target DNA and have a critical role in the specificity of the PCR reaction. An appropriate primer design is one of the most important factor for good PCR. A poorly designed primer can result in little or no target product, due to non-specific amplification or primer dimer formation leading to reaction failure, even when all the other parameters are properly optimized. There are number of criteria such as primer length, Tm, GC contents, 3'-end sequence, 5'-end sequence, primer-dimer formation, hairpin-loop structure formation that need to be established in the design of primers to have efficient primers for PCR reaction. This article provides general guidelines for PCR primer design.