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प्रश्न
Explain briefly:
Restriction enzymes and DNA
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उत्तर
Restriction enzymes are used to break up DNA molecules. They are part of a broader enzyme class known as nucleases. Restriction enzymes are classified into three types:
- Exonucleases: They remove nucleotides from the terminal ends (5' or 3') of one double strand of DNA.
- Endonucleases: They make cuts at specific positions within the DNA. These enzymes don’t fragment the ends and only affect one strand of the DNA helix.
- Restriction endonucleases: Arber identified them in bacteria in 1963. They function as “molecular scissors” or chemical scalpels. They detect the base sequence at palindrome sites in DNA sequences and sever the strands. There are three types of restriction endonucleases: type I, type II, and type III. Only type II restriction enzymes are utilised in recombinant DNA technology because they can recognise and cut inside a specified DNA sequence, typically consisting of 4 to 8 nucleotides.
APPEARS IN
संबंधित प्रश्न
How are 'sticky ends' formed on a DNA strand? Why are they so called?
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.
How does a restriction nuclease function? Explain
Make a chart (with diagrammatic representation) showing a restriction enzyme, the substrate DNA on which it acts, the site at which it cuts DNA and the product it produces.
Distinguish between exonuclease and endonuclease.
How does restriction endonuclease function?
Explain the roles of the following with the help of an example each in recombinant DNA technology :
Restriction Enzymes
Answer the following question.
Explain the significance of palindromic nucleotide sequence in the formation of recombinant DNA.
Give a reason why :
Single cloning site is preferred in a vector.
A mixture containing DNA fragments a, b, c and d, with molecular weights of a + b = c, a > b and d > c was subject to agarose get electrophoresis. This position of these fragments from cathode to anode to anode sides of the gel would be ______.
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 ______
'Restriction' in Restriction enzyme refers to ______.
In agarose gel electrophoresis, DNA molecules are separated on the basis of their ______.
Which of the following bacteria is not a source of restriction endonuclease?
What does H in’ ‘d’ and ‘III’ refer to in the enzyme Hind III?
Restriction enzymes should not have more than one site of action in the cloning site of a vector. Comment.
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.
How does one visualise DNA on an agarose gel?
CTTAAG
GAATTC
- What are such sequences called? Name the enzyme used that recognizes such nucleotide sequences.
- What is their significance in biotechnology?
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
Given below is the restriction site of a restriction endonuclease Pst-I and the cleavage sites on a DNA molecule.
\[\ce{5' C - T - G - C - A \overset{\downarrow}{-}{G 3'}}\]
\[\ce{3' G\underset{\uparrow}{-} A - C - G - T - C 5'}\]
Choose the option that gives the correct resultant fragments by the action of the enzyme Pst-I.
What are the protruding and hanging stretches of DNA produced by these restriction enzymes called? Describe their role in the formation of rDNA.
State the principle involved in separation of DNA fragments using gel electrophoresis.
Identify the activity of endonuclease and exonuclease in the given image.
