1. Assume that those DNA molecules are same in length as well as in other properities such as supercoiling...etc, in gel after electrophoresis, we can observe one thick band. 2. As DNA is -vely charged molecules due to P- ions, if the electrodes connects in wrong direction, it won\'t enter in to gel. Those molecules sometimes may migrate to buffer chambers. Solution 1. Assume that those DNA molecules are same in length as well as in other properities such as supercoiling...etc, in gel after electrophoresis, we can observe one thick band. 2. As DNA is -vely charged molecules due to P- ions, if the electrodes connects in wrong direction, it won\'t enter in to gel. Those molecules sometimes may migrate to buffer chambers..