Question

Which of the following is incorrect regarding gel electrophoresis after PCR amplification of gene of interest?

• A. Determination of location of DNA with gene of interest on the gel requires the presence of ladder
• B. Determination of location of DNA with gene of interest on the gel does not require the presence of ladder
• C. Markers are present in the form of ladder which signify molecular weight of DNA molecules
• D. Markers contain DNA fragments of known molecular weight which get separated to form known standards

Answer 1

The correct option is B Determination of location of DNA with gene of interest on the gel does not require the presence of ladder

A DNA ladder is a mixture of DNA molecules of different lengths of known molecular weights. It is pipetted in the first well of the agarose gel. This gets separated in the first lane according to the molecular size under the influence of the electric field. Markers are present in the form of ladder which signify molecular weight of DNA molecules. It is used as a reference to estimate the size of the sample DNA molecules being separated under the same experimental conditions. Hence, the band containing the DNA with the gene of interest whose approximate molecular weight is known, can be identified by comparing it to the ladder.


If our gene of interest (GOI) in column A is expected to contain 1000bp, then the band in lane A which corresponds to 1000bp is expected to be the one containing the gene of interest.