What is the use of a “ladder” on a gel electrophoresis?
When there is a mixture of nucleic acids and proteins, they can be separated according to their molecular size and electrical charge by a technique called gel electrophoresis. The most commonly used types of gels in gel electrophoresis are agarose and polyacrylamide gels.
The gel is punched to form indentations called wells on one side where the samples are loaded. The gel is subjected to an electric field by connecting one end of the gel to the positive electrode and the other end to the negative electrode. The gel is immersed in a buffer solution that conducts electricity. On application of an electric field, the larger molecules travel slowly through the pores of the gel while the smaller molecules enter and exit the pores of the gel quickly. The molecules of different sizes in the sample mixture get separated and appear as distinct bands on the gel.
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