`("amp")^( R)` in vector pBR322 indicates:

Options

A. Gene responsible for synthesis of ampicillin
B. Gene conferring resistance against ampicillin
C. Palindromic DNA sequence for EcoRI
D. Amplified DNA

Answer

To solve the question regarding what `("amp")^( R)` in vector pBR322 indicates, let's break down the components step by step:

### Step 1: Understanding the Vector pBR322
- **Definition**: pBR322 is a plasmid vector used in molecular biology for cloning purposes. It is designed to carry foreign DNA into a host cell.
- **Components**: It contains multiple cloning sites and genes that confer resistance to antibiotics, which are crucial for selecting transformed cells.

### Step 2: Identifying the Components of `("amp")^( R)`
- **"amp"**: This stands for ampicillin, an antibiotic.
- **"R"**: This indicates resistance.

### Step 3: Interpreting `("amp")^( R)`
- The notation `("amp")^( R)` specifically refers to the gene in the pBR322 vector that provides resistance to the antibiotic ampicillin.
- This means that the presence of this gene allows bacterial cells that have taken up the pBR322 vector to survive in an environment containing ampicillin.

### Step 4: Analyzing the Options
- **Option A**: Gene responsible for synthesis of ampicillin - This is incorrect because the gene does not synthesize ampicillin; it provides resistance to it.
- **Option B**: Gene conferring resistance against ampicillin - This is correct as it directly describes the function of the `("amp")^( R)` component.
- **Option C**: Palindromic DNA sequence for EcoR1 - This is incorrect; EcoR1 is a restriction enzyme, not related to ampicillin resistance.
- **Option D**: Amplified DNA - This is also incorrect as it does not pertain to the specific function of the `("amp")^( R)`.

### Conclusion
The correct answer is **Option B: Gene conferring resistance against ampicillin**.

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