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प्रश्न
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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उत्तर
It is because plasmid is a circular DNA molecule. When cut with enzyme, it becomes linear but does not get fragmented. Whereas, a linear DNA molecule gets cut into two fragments. Hence, a single DNA band is observed for plasmid while two DNA bands are observed for linear DNA in agarose gel.

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संबंधित प्रश्न
Mention the difference in the mode of action of exonuclease and endonuclease.
Suggest a technique to a researcher who needs to separate fragments of DNA.
Name and describe the technique that helps in separating the DNA fragments formed by the use of restriction endonuclease
Collect 5 examples of palindromic DNA sequences. Better try to create a palindromic sequence by following base-pair rules.
Distinguish between exonuclease and endonuclease.
Explain the roles of the following with the help of an example each in recombinant DNA technology :
Restriction Enzymes
Answer the following question.
Write the use of restriction endonuclease in the formation of recombinant DNA.
The DNA fragment separated on an agarose gel can be visualized by staining with ______.
There is a restriction endonudease called as EcoRI. What does co part in it stands for?
DNA strands on a gel stained with ethidium bromide when viewed under UV radiation, appear as ______
A specific recognition sequence identified by endonucleases to make cuts at specific positions within the DNA is ______
Which of the given statements is correct in the context of visualizing DNA molecules separated by agarose gel electrophoresis?
In agarose gel electrophoresis, DNA molecules are separated on the basis of their ______.
The role of DNA ligase in the construction of a recombinant DNA molecule is ______.
What does H in’ ‘d’ and ‘III’ refer to in the enzyme Hind III?
CTTAAG
GAATTC
- What are such sequences called? Name the enzyme used that recognizes such nucleotide sequences.
- What is their significance in biotechnology?
Carefully observe the given picture. A mixture of DNA with fragments ranging from 200 base pairs to 2500 base pairs was electrophoresed on agarose gel with the following arrangement.

(a) What result will be obtained on staining with ethidium bromide? Explain with reason.
(b) The above setup was modified and a band with 250 base pairs was obtained at X.

What change(s) were made to the previous design to obtain a band at X? Why did the band appear at position X?
Given below is the stepwise schematic representation of the process of electrophoresis. Identify the 'alphabets' representing
- Anode end
- smallest/lightest DNA strand in the matrix
- Agarose gel

How are DNA fragments visualised once they are separated by gel electrophoresis?
