Subjective Type

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?

Solution

Following are the possible reasons for non-observation of DNA bands:
(a) The gel plate was not exposed to UV light.
(b) Electrodes may have been put in wrong orientation; with anode towards the loading well.
As DNA is negatively charged, It moves towards anode. When anode is near the loading well, separated DNA may move out of the gel.
c) The sample may be contaminated with protein or RNA
d) Improper loading of the sample in the wells.

SIMILAR QUESTIONS

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Having become an expert on gel electrophoresis, you are asked to examine a gel for a colleague. Where would you find the smallest segments of DNA?

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Which of the following steps should be performed by a person in order to visualise the bands of DNA fragments obtained from gel electrophoresis?

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Select the correct option to fill up the blanks. (i) _____ is a natural polymer extracted from ______. (ii) The DNA fragments purified by gel electrophoresis are used in constructing _____ by joining them with ______. (iii) The ligation of alien DNA is carried out at a _____ present in one of the two ____ in a plasmid vector. (iv) _____ enzyme remains active during the high temperature-induced denaturation of ds DNA. DNA fragments are resolved according to their ______ (v) through _____ in agarose gel electrophoresis.

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A plasmid DNA and a linear DNA (both are of the same size) have one site for a restriction endonuclease. When cut and separated on agarose gel electrophoresis, plasmid shows one DNA band while linear DNA shows two fragments. Explain.

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How does one visualise DNA on an agarose gel?

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