Restriction enzymes produced by some bacteria:
1. | cleave phosphodiester bond in the main chromosomal DNA of the bacterium. |
2. | cut single stranded DNA at random positions. |
3. | prevent the multiplication of bacteriophage in bacteria. |
4. | provide resistance against antibiotics. |
The DNA fragments separated on agar gel by electrophoresis can be visualised:
1. | without staining in the visible light |
2. | without staining on exposure to UV light |
3. | after staining with polyethylene glycol followed by exposure to IR radiation |
4. | after staining with ethidium bromide followed by exposure to UV radiation |
If an enzyme catalyses the removal of nucleotides from the ends of DNA, then it should be called as:
1. endonuclease
2. exonuclease
3 ligase
4. reverse transcriptase
A plasmid has a single recognition sequence for EcoRI. When cut with this enzyme, the number of resultant fragments will be:
1. 1
2. 2
3. 3
4. 4
a: | DNA fragments are negatively charged molecules and can be separated by forcing them to move towards the anode under an electric field through a medium/matrix. |
b: | The separation of DNA fragments is possible because they differ in size. |
c: | Smaller the size of the DNA fragment, shorter the distance it travels through agarose gel. |
d: | Pure DNA can be visualized directly by exposing it to UV radiation without any staining. |