What is the specific catalytic function of restriction endonucleases (restriction enzymes) in genetic engineering?
Answer and explanation
Correct answer: B. Cleaving DNA at specific palindromic recognition sequences
- Step 1: Recall the mechanism of restriction enzymes: bacterial enzymes evolved to protect against viral bacteriophages by degrading foreign nucleic acids.
- Step 2: They recognize specific symmetrical palindromic base sequences (e.g., for EcoRI) and cleave phosphodiester bonds, generating 'sticky ends' or blunt ends.
Answer
Cleaving DNA at specific palindromic recognition sequences.
Why not the others: 'Joining complementary sticky ends of DNA fragments using phosphodiester bonds' is the function of DNA ligase; 'Synthesizing complementary DNA strands from an RNA template' is the function of reverse transcriptase; 'Unwinding the double helix during DNA transcription' is performed by DNA helicase / RNA polymerase.
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