Electrophoresis of PCR Products

To visualize the samples on the gel, when placing them into the wells, visible dyes that can be seen under UV light, such as DNA Safe Stain, are used. In the past, ethidium bromide was used for staining; however, due to its toxicity and mutagenicity, its use in laboratories has been prohibited. After the molecules have migrated to the opposite pole, the electric current is turned off, and the gel is imaged using a device known as a gel doc.

With this technique, users can identify DNA molecules of varying lengths. Since DNA molecules carry a negative charge, they migrate towards the positive electrode when placed on the gel and subjected to an electric current. In this context, the separation of DNA molecules occurs based solely on their size. Shorter DNA strands move faster than longer molecules, making the separation of DNA molecules of different sizes easier. As previously mentioned, tracking the samples is performed by adding fluorescent dyes into the gel wells. Some users mix the fluorescent dyes with the gel just before transferring it to the electrophoresis apparatus, which eliminates the need to add dye when loading the samples. Electrophoresis for DNA molecules is performed horizontally, which is a simpler method compared to the vertical approach.

After the current is stopped, the bands of DNA molecules of different sizes become visible on the gel. To determine the size of the sample bands, a marker or ladder is used as a standard. The ladder appears on the gel as bands of defined lengths, allowing for the assessment of the sizes of the sample bands on the gel.