I am using Universal primer set (LCO1490 and HCO2198) to identify Culex mosquito species (tritaeniorhynchus and quinquefasciatus) by using COX gene. the expected product size was 710 bp but after gradient PCR. when i ran samples on gel i got two bands for each sample. i.e at around 300 bp and the other one was at around 500 bp. GC content for both primers is < 35%.