In Lederberg's replica what shall be used to obtain streptomycin resistant strain ?

Options

A. Minimal medium and streptomycine
B. Complete medium and streptomycine
C. Only minimal medium
D. Only complete medium

Answer

To solve the question regarding Lederberg's replica experiment and the medium used to obtain a streptomycin-resistant strain, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Purpose of the Experiment**:
- The Lederberg replica plating experiment aimed to demonstrate the nature of mutations in bacteria, specifically showing that mutations are random and not directed by environmental factors.

2. **Identify the Types of Medium Used**:
- In the experiment, two types of media were used:
- **Complete Medium**: This medium contains all necessary nutrients for bacterial growth, allowing all bacteria to grow regardless of their resistance to antibiotics.
- **Selective Medium (Minimal Medium)**: This medium has minimal nutrients and includes a specific antibiotic (in this case, streptomycin). It allows only the bacteria that are resistant to the antibiotic to grow.

3. **Analyze the Growth on Each Medium**:
- On the **Complete Medium**, all bacterial colonies grow, including both resistant and non-resistant strains.
- On the **Selective Medium**, only the streptomycin-resistant colonies survive and grow, as the antibiotic kills the non-resistant strains.

4. **Conclude the Correct Medium for Obtaining Resistant Strains**:
- Since the question specifically asks for the medium used to obtain the streptomycin-resistant strain, the answer is the **Selective Medium (Minimal Medium) with streptomycin**.

5. **Final Answer**:
- The correct answer to the question is **Selective Medium (Minimal Medium) + Streptomycin**.