Question

Most commonly used enzymes for DNA manipulation include the following
A. Nucleases
B. Ligases
C. Polymerases
D. Kinases
E. Helicases
Choose the most appropriate answer from the options given below:

• A. A, D and E only
• B. B, D and E only
• C. A, B and C only
• D. C, D and E only

Hint:

Remember the "CLAM" analogy: Cut (Nucleases), Ligate (Ligases), Amplify (Polymerases).
These three categories cover the vast majority of cloning and diagnostic molecular biology workflows.

Answer 1

The Correct Option is C

Step 1: Understanding the Question:
The question asks to identify the fundamental enzymatic tools used in recombinant DNA technology (Genetic Engineering). These enzymes are often referred to as the "biological toolkit" for cutting, joining, and copying DNA fragments.

Step 2: Detailed Explanation:

• Nucleases (A): These are "molecular scissors." Restriction endonucleases are the most commonly used for manipulation as they cut DNA at specific palindromic sequences, creating "sticky" or "blunt" ends. This allows for precise excision of genes of interest.

• Ligases (B): These are "molecular glue." DNA ligase (especially T4 DNA ligase) is essential for joining two DNA fragments together by catalyzing the formation of a phosphodiester bond between the 3'-OH and 5'-phosphate ends. This is the critical step in creating recombinant vectors.

• Polymerases (C): These enzymes synthesize new strands of DNA complementary to a template. Taq polymerase is the star of PCR (amplification), while others like the Klenow fragment are used for filling in sticky ends or labeling DNA probes.

• Other Enzymes (D and E): While Kinases (like Polynucleotide Kinase) add phosphates and are used in labeling, they are considered specialized. Helicases (E) unwind DNA in nature but are rarely used as "tools" for manipulation in a test tube because heat or chemical denaturation is more efficient and standard.
Final Answer:
The "Big Three" enzymes that form the core of standard DNA manipulation protocols are Nucleases, Ligases, and Polymerases. Therefore, A, B, and C only is the most appropriate choice.