There are 5 test tubes having a culture medium containing rough colonies of streptococcus pneumoniae. The following substances were added in them. Which of these test tubes will show smooth colonies of streptococcus pneumoniae on incubation for some time?
Test tube I: RNA from a heat-killed smooth strain of streptococcus pneumoniae
Test tube II: DNA from a heat-killed smooth strain of streptococcus pneumoniae
Test tube III: Protein from a heat-killed smooth strain of streptococcus pneumoniae
Test tube IV: Carbohydrate from a heat-killed smooth strain of streptococcus pneumoniae
Test tube V: Heat killed smooth strain of streptococcus pneumoniae incubated with DNAse enzyme

Options

A. II and V
B. II , III and IV
C. I and II
D. II

Answer

To solve the question regarding which test tube will show smooth colonies of Streptococcus pneumoniae after incubation, we need to understand the concept of transformation and the role of genetic material in determining the characteristics of bacterial colonies.

### Step-by-Step Solution:

1. **Understand the Types of Streptococcus pneumoniae**:
- There are two types of Streptococcus pneumoniae:
- **Smooth (S) strain**: This strain is virulent and has a polysaccharide capsule that protects it from the immune system.
- **Rough (R) strain**: This strain is non-virulent and lacks the protective capsule.

2. **Transformation Process**:
- Transformation is a process where a bacterium takes up foreign DNA from its environment and incorporates it into its own genome, potentially acquiring new traits, such as virulence.

3. **Analyze Each Test Tube**:
- **Test Tube I**: Contains RNA from a heat-killed smooth strain.
- **Outcome**: RNA does not carry the genetic information necessary for transformation. Therefore, no smooth colonies will form.

- **Test Tube II**: Contains DNA from a heat-killed smooth strain.
- **Outcome**: The DNA can be taken up by the rough strain, allowing it to acquire the smooth strain's characteristics. Thus, smooth colonies will form in this test tube.

- **Test Tube III**: Contains protein from a heat-killed smooth strain.
- **Outcome**: Proteins do not have the genetic information needed for transformation. Therefore, no smooth colonies will form.

- **Test Tube IV**: Contains carbohydrate from a heat-killed smooth strain.
- **Outcome**: Carbohydrates do not carry genetic information. Thus, no smooth colonies will form.

- **Test Tube V**: Contains heat-killed smooth strain incubated with DNase enzyme.
- **Outcome**: DNase will degrade the DNA, preventing any transformation from occurring. Therefore, no smooth colonies will form.

4. **Conclusion**:
- The only test tube that will show smooth colonies of Streptococcus pneumoniae after incubation is **Test Tube II**, which contains DNA from a heat-killed smooth strain.

### Final Answer:
**Test Tube II** will show smooth colonies of Streptococcus pneumoniae after incubation.

---