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प्रश्न
Explain briefly:
Restriction enzymes and DNA
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, endonucleases, and restriction endonucleases.
- 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.
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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.
How does a restriction nuclease function? Explain
Collect 5 examples of palindromic DNA sequences. Better try to create a palindromic sequence by following base-pair rules.
Distinguish between exonuclease and endonuclease
Answer the following question.
Write the use of restriction endonuclease in the formation of recombinant DNA.
Give a reason why :
Single cloning site is preferred in a vector.
The DNA fragment separated on an agarose gel can be visualized by staining with ______.
DNA strands on a gel stained with ethidium bromide when viewed under UV radiation, appear as ______
'Restriction' in Restriction enzyme refers to ______.
The role of DNA ligase in the construction of a recombinant DNA molecule is ______.
Would you choose an exonuclease while producing a recombinant DNA molecule?
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 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?
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
What is elution?
What are the protruding and hanging stretches of DNA produced by these restriction enzymes called? Describe their role in the formation of rDNA.
How are DNA fragments visualised once they are separated by gel electrophoresis?
Identify the activity of endonuclease and exonuclease in the given image.
