How to avoid smear in your Gel Electrophoresis

How to avoid smear in your gel Electrophoresis: 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 cross-contamination. Sometimes 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. It is advisable to re-run your sample and compare the outcome. 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. 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 DNA added, or the amount of MgCl used, or reduce the amount of Taq Polymerase or the number of cycles. 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, amplifying a smear. However, too much template seems more likely based on the information provided. It's important to note that the order of the advice may vary depending on the specific context and information provided in the experiment. If additional information becomes available, it may be necessary to reassess and reorder the advice accordingly. #dna #rna #gelelectrophoresis #genetics #pcr #biology