Restriction enzymes do not act on the DNA of the host cell in which they are produced, because :

1.  Host DNA is packed into chromosomes
2.  Restriction enzymes are ineffective on host DNA
3.  Host DNA does not have the restriction site for the restriction enzymes.
4.  Restriction site of host DNA is methylated.

Subtopic:  Restriction Enzymes - Main Enzymes |
 72%
Level 2: 60%+
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In the first gene cloning experiment:

1.  Researchers successfully identified a human gene responsible for the disease.
2.  Researchers successfully inserted a gene for kanamycin resistance into a plasmid vector.
3.  Researchers demonstrated that many different DNA fragments could insert into a plasmid vector
4.  Researchers produced a strain of bacteriophage with an increased ability to infect E. coli.
Subtopic:  Restriction Enzymes - Main Enzymes |
Level 3: 35%-60%
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A circular plasmid of 10000 bp is digested with two restriction enzymes A and B, to produce 3000 bp and 2000 bp bands when visualized on an agarose gel. When digested with one enzyme at a time, only one band is visible at 5000 bp. If the first site for enzyme A [A1] is present at the 100th base, the order in which the remaining sites [A2, B1 and B2] are present is: 

1.5100, 3100, 81002.3100, 5100, 8100
3.8100, 5100, 31004.8100, 3100, 5100

Subtopic:  Restriction Enzymes - Main Enzymes |
Level 3: 35%-60%
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When the phage DNA enters a bacterium, it protects itself from the viral DNA with the help of:

1.  methylases 2.  endonucleases
3.  exonucleases 4.  ligases

Subtopic:  Restriction Enzymes - Main Enzymes | Restriction Enzymes: Historical Background |
Level 3: 35%-60%
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What is the problem in providing a bone marrow transplant to a patient of SCID as a treatment?

1. rejection of the graft by the recipient

2. graft-versus-host disease

3. cardiovascular failure

4. anaphylaxis

Subtopic:  Restriction Enzymes - Main Enzymes | Transforming Plant & Animal Cell | Obtaining Copy of Gene from Donor DNA | Restriction Enzymes: Historical Background |
Level 4: Below 35%
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