constructing a dna ladder range for lambda phage by multiplex pcr

background and objectives: dna ladder contains dna fragments of different length but with known size, used to determine the size of unknown dna molecules. different dna ladders are available for expected dna length. conserved sequences were selected for design of primers to generate dna fragments of known specific size. materials and methods: in this study, we describe a method by which dna ladder was prepared based on multiplex pcr technique. different lengths of dna fragments were amplified using the primers designed according to the 1216-2136 sequence extent of lambda phage dna. target dna fragments were amplified using multiplex pcr and extracted. results: the results showed an amplified lambda phage dna at particular target sites by using 1 forward and 6 different reverse primers (for 100, 200, 400, 600, 800, 1000bp) for the successful amplification. conclusion: this method would be more cost effective than commercial dna molecular weight markers.