Ernest chain and Howared Florey's contribution was

Options

A. discovery of streptokinase
B. establishing the potential of penicillin as an effective antibiotic
C. discovery of the DNA sequences
D. isolating the bacterial plasmid

Answer

### Step-by-Step Text Solution:

1. **Identify the Contributors**: The question asks about the contributions of Ernst Chain and Howard Florey. Both scientists are known for their work in the field of antibiotics.

2. **Understand Their Contribution**: Ernst Chain and Howard Florey played a pivotal role in establishing the effectiveness of penicillin as an antibiotic. They conducted research that demonstrated how penicillin could be used to treat bacterial infections.

3. **Historical Context**: Penicillin was discovered by Alexander Fleming, but it was Chain and Florey who worked on its development and mass production during World War II. Their work was crucial in making penicillin widely available for medical use.

4. **Evaluate the Options**:
- **Option A**: Discovery of streptokinase - This is incorrect; streptokinase was discovered by Dr. William Smith Tidwell.
- **Option B**: Establishing the potential of penicillin as an effective antibiotic - This is the correct answer.
- **Option C**: Discovery of DNA sequences - This was done by Frederick Sanger, not Chain and Florey.
- **Option D**: Isolating the bacterial plasmid - There is no contribution from Chain and Florey in this area.

5. **Conclusion**: Based on the evaluation of the options, the correct answer is **Option B: Establishing the potential of penicillin as an effective antibiotic**.