This is my first time doing agarose gel elephoresis on pcr. I want to ask what are the smear lines in lane 4 and 7?
It could be that you are adding too much dna template and it is degraded or contains a lot of rna.Running an unamplified dna sample would tell you if this is the case. It might also be that one of your primers has homology with a repeat sequence and that one primer is binding in many places in both orientations and amplifying a smear but too much template seems the more likely
It is not clear for me whether lane 1 of your gel represents a negative control? If you have run a negative control (i.e. no DNA template is added) and you also got amplicons or smears, then this may indicate a cross- contamination. Otherwise, smears can develop mostly due to bad quality primers or may be a low T(a). Sometimes you may need to reduce the amount of your DNA added, or the amount of MgCl used or reduce the amount of TaqPolymerase or number of cycles.
Best Wishes
some times when your sample is not properly digested, you may experience a smear line. Contaminants or hairpin caused as a result of homology can also give a smear. is is advisable to re-run your sample and compare the outcome.
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