A mixture of fragmented DNA was electrophoresed in an agarose gel. After staining the gel with ethidium bromide, no DNA bands were observed. What could be the reason?
DNA bands may not be observed when a mixture of fragmented DNA was electrophoresed, due to following reasons:
(i) Concentration of agarose in the gel was not proper, as greater the concentration of agarose gel used, the greater will be the facilitation of the separation of small DNA fragments, whereas smaller the concenration of agarose higher will be the resolution of bands.
(ii) If the concentration of salt in the buffer was not proper.
(iii) If DNA sample is contaminated with RNA or any other impurity or if the concentration of DNA is too low.