Which of the following is not a recombinant protein used in medical practice ?

Options

A. A. TPA (Tissue plasminogen activator)
B. B. Interferon
C. C. Vaccine for hepatitis B
D. D. Crystal proteins

Answer

To determine which of the following is not a recombinant protein used in medical practice, we will analyze each option provided:

1. **TPA (Tissue Plasminogen Activator)**:
- TPA is a protein that is used to dissolve blood clots. It is produced through recombinant DNA technology, making it a recombinant protein. Therefore, TPA is not the correct answer.

2. **Interferon**:
- Interferons are proteins that play a role in the immune response and are used to treat various diseases, including some cancers and viral infections. Interferons are also produced using recombinant DNA technology, so this option is not correct either.

3. **Vaccine for Hepatitis B**:
- The hepatitis B vaccine is produced using recombinant DNA technology. It contains a protein that is similar to the surface antigen of the hepatitis B virus, which helps the immune system recognize and fight the virus. Thus, this option is also not the answer.

4. **Crystal Protein**:
- Crystal proteins, specifically those produced by the bacterium *Bacillus thuringiensis*, are not recombinant proteins. They are naturally occurring proteins that have insecticidal properties and are used in agriculture but are not produced through recombinant DNA technology.

Based on the analysis, the correct answer is **D: Crystal Protein**, as it is not a recombinant protein used in medical practice.

### Summary of Steps:
1. Analyze TPA: Confirm it is a recombinant protein.
2. Analyze Interferon: Confirm it is a recombinant protein.
3. Analyze Hepatitis B Vaccine: Confirm it is a recombinant protein.
4. Analyze Crystal Protein: Confirm it is not a recombinant protein.