Question

A mixture of fragmented DNA was electrophoresed in agarose gel. After staining the gel with ethidium bromide, no DNA bands were observed. What could be the reason?

Answer 1

A mixture of fragmented DNA was electrophoresed in an agarose gel. A mixture of fragmented DNA was electrophoresed in an agarose gel. After staining the gel with ethidium bromide, no DNA bands were observed. ... (iii) If DNA sample is contaminated with RNA or any other impurity or if the concentration of DNA is too low.

Answer 2

❣️$\huge\underline\mathfrak{heya}$❣️

The reasons are as follows:

➡️ (i) DNA sample that was loaded on the gel may have got contaminated with nuclease (exo-or endo-or both) and completely degraded.

➡️ (ii) Electrodes were put in opposite orientation in the gel assembly that is anode towards the wells (where DNA sample is loaded). Since DNA molecules are negatively charged, they move towards anode and hence move out of the gel instead of moving into the matrix of gel.

➡️ (iii) Ethidium bromide was not added at all or was not added in sufficient concentration and DNA was not visible .

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