Subjective Type

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.

Solution

When treated with a restriction endonuclease circular DNA opens up to resemble a single linear DNA. A Linear DNA is divided into two fragments after cleavage. Hence, circular DNA shows one band, while linear DNA shows two bands when run on agarose gel electrophoresis.

SIMILAR QUESTIONS

Biotechnology

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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How does one visualise DNA on an agarose gel?

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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?

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