Question

The cutting of DNA at specific locations became possible with the discovery of -

• A. Reverse transcriptase
• B. Restriction endonuclease
• C. Bacteriophage
• D. P. C. R.

Hint:

Remember the key tools of genetic engineering and their functions: {Cutting DNA:} Restriction Endonucleases {Pasting DNA:} DNA Ligase {Copying DNA:} DNA Polymerase (used in PCR) {Making DNA from RNA:} Reverse Transcriptase

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
The question asks about the discovery that enabled scientists to cleave DNA molecules at precise, predictable sites, a foundational technique for genetic engineering.
Step 2: Detailed Explanation:
Reverse transcriptase: An enzyme that synthesizes DNA from an RNA template. It is used to create complementary DNA (cDNA) but does not cut DNA.
Restriction endonuclease: Also known as a restriction enzyme, this is a protein that recognizes a specific short nucleotide sequence (the restriction site) and cuts the DNA molecule at or near that site. Their discovery allowed for the precise cutting and pasting of DNA, launching the era of recombinant DNA technology. They act as "molecular scissors."
Bacteriophage: A virus that infects bacteria. While some phages are sources of useful enzymes or are used as cloning vectors, the phage itself is not the tool for cutting DNA.
P. C. R. (Polymerase Chain Reaction): A technique used to amplify a specific segment of DNA, creating millions of copies. It involves DNA synthesis, not cutting.
Step 3: Final Answer:
The discovery of restriction endonucleases made the specific cutting of DNA possible.