Which of the following statement is incorrect ?

Options

A. Cosmid contains gene coding for viral protein
B. Cosmid replicates like plasmids
C. Cosmid has antibiotic resistant marker gene
D. Cos site has 12 bases helping to join complete genome to make it circular

Answer

To solve the question regarding which statement is incorrect about Cosmid, we will analyze each of the provided statements step by step.

### Step-by-Step Solution:

1. **Understanding Cosmid**:
- Cosmid is a type of vector used in molecular biology, primarily for cloning DNA fragments. It is derived from the lambda phage and is designed to carry larger DNA inserts than standard plasmids.

2. **Analyzing the Statements**:
- **Statement 1**: "Cosmid contains gene coding for viral protein."
- This statement is incorrect. Cosmids are designed to carry human or other eukaryotic genes, not viral proteins. Therefore, this statement is false.

- **Statement 2**: "Cosmid replicates like plasmid."
- This statement is correct. Cosmids replicate in a manner similar to plasmids, as they both utilize the host's replication machinery.

- **Statement 3**: "Cosmid has antibiotic resistant marker."
- This statement is also correct. Cosmids typically contain antibiotic resistance genes, such as those for ampicillin or tetracycline, which allow for the selection of successfully transformed cells.

- **Statement 4**: "Cosmid has 12 base pairs helping to join complete genome to make it circular."
- This statement is correct. Cosmids have a cos sequence that is 12 base pairs long, which is essential for the circularization of the DNA.

3. **Conclusion**:
- The only incorrect statement among the options is the first one, which claims that cosmids contain genes coding for viral proteins. Therefore, the answer to the question is that the first statement is incorrect.

### Final Answer:
- The incorrect statement is: "Cosmid contains gene coding for viral protein."