Given below are two statements : Statement I: Restriction endonucleases are enzymes naturally found in bacteria, where they protect the host cell by degrading foreign DNA. Statement II: All restriction endonucleases cut both strands of the DNA molecule at the exact same position, producing 'blunt ends'. In the light of the above statements, choose the most appropriate answer from the options given below:
Analyzing Restriction Endonuclease Statements
This question requires evaluating two statements about restriction endonucleases, commonly used enzymes in molecular biology.
Understanding Statement I: Role of Restriction Endonucleases
Statement I correctly identifies restriction endonucleases as enzymes primarily found in bacteria. Their natural function is a defense mechanism against foreign DNA, such as that from viruses (bacteriophages). They achieve this by recognizing specific DNA sequences and cleaving the foreign DNA, thus protecting the host bacterium.
- Restriction enzymes are part of the bacterial immune system.
- They degrade foreign DNA.
- This protects the host cell.
Evaluating Statement II: DNA Cutting Patterns
Statement II claims that all restriction endonucleases cut both DNA strands at the exact same position, producing only blunt ends. This is factually incorrect.
- While some restriction enzymes do cut symmetrically, producing blunt ends (e.g., SmaI), many others do not.
- Most restriction enzymes cut the two DNA strands at slightly different positions.
- These staggered cuts result in short, single-stranded overhangs called sticky ends (e.g., EcoRI, HindIII).
- Therefore, the generalization that all restriction enzymes produce blunt ends is false.
Conclusion: Selecting the Correct Option
Based on the analysis:
- Statement I is correct.
- Statement II is incorrect.
This corresponds to the option stating that Statement I is correct and Statement II is incorrect.
Final Answer: The final answer is Statement I is correct but Statement II is incorrect
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