In cystic fibrosis there is

Options

A. Failure of chloride ion transport
B. Mucous clogging of lungs
C. Defective functioning
D. All the above

Answer

### Step-by-Step Solution

1. **Understanding Cystic Fibrosis**: Cystic fibrosis is a genetic disorder that primarily affects the lungs and digestive system. It is caused by mutations in the CFTR gene.

2. **Identifying the CFTR Gene**: The CFTR gene (Cystic Fibrosis Transmembrane Conductance Regulator) is located on the long arm of chromosome 7. This gene is responsible for coding the CFTR protein, which functions as a chloride ion channel.

3. **Function of CFTR Protein**: The CFTR protein plays a crucial role in transporting chloride ions across cell membranes. This transport is essential for the production of sweat, digestive juices, and mucus.

4. **Effects of Mutations**: Mutations in the CFTR gene lead to the production of a defective CFTR protein. This defective protein does not allow chloride ions to pass through the cell membrane effectively.

5. **Consequences of Defective CFTR**: When the CFTR protein is malfunctioning, chloride ions cannot flow in and out of the cells properly. This results in:
- **Failure of Chloride Ion Transport**: The primary defect in cystic fibrosis is the inability to transport chloride ions.
- **Mucus Build-Up**: The malfunction leads to the accumulation of thick mucus in the lungs and other organs, causing severe respiratory issues.
- **Clogging of Lungs**: The thick mucus clogs the airways, making it difficult to breathe and increasing the risk of lung infections.
- **Defective Functioning**: Overall, the malfunctioning of the CFTR protein results in defective functioning of various organs, particularly the lungs and digestive system.

6. **Conclusion**: Given the above points, the correct answer to the question "In cystic fibrosis there is" is "all the above," as it encompasses failure of chloride ion transport, mucus build-up, and clogging of the lungs, along with defective functioning of the affected organs.