Lederberg and Lederberg demonstrated that mutations are preadaptive. They used the following technique for the purpose

Options

A. Replica plating
B. Gene sequencing
C. Transduction
D. Transformation

Answer

**Step-by-Step Solution:**

1. **Introduction to the Experiment**: Lederberg and Lederberg aimed to demonstrate that mutations in bacteria can occur in advance of exposure to selective pressures, such as antibiotics. They specifically focused on penicillin resistance.

2. **Selection of Bacterial Strains**: They selected two different colonies of bacteria, which we will refer to as Colony X and Colony Y. These colonies were used to study the mutations that could confer resistance to penicillin.

3. **Replica Plating Technique**: The key technique used in their experiment was called "replica plating." This method allowed them to transfer the bacteria from one plate to another while maintaining the spatial arrangement of the colonies.

4. **Plating the Colonies**: They plated Colony X on one agar plate and Colony Y on another agar plate. This step was crucial as it allowed them to observe the growth patterns of the bacteria in response to the antibiotic.

5. **Exposure to Penicillin**: After plating, they exposed the bacteria to penicillin. The goal was to see which colonies had developed mutations that made them resistant to the antibiotic.

6. **Observation of Results**: After the exposure, they observed the growth of the colonies. Some colonies showed resistance to penicillin, indicating that mutations had occurred prior to the exposure to the antibiotic.

7. **Conclusion**: The results of the experiment demonstrated that mutations can occur independently of the selective pressure. This provided evidence for the concept of pre-adaptation, where mutations that confer an advantage can exist in a population before the selective pressure is applied.

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