Mutations in the CFTR gene result in cystic fibrosis in humans, a condition in which abnormal secretions are present in the lungs, pancreas, and sweat glands. The gene was mapped to a 500-kb region on chromosome 7 containing three candidate genes.
Using your knowledge of the disease symptoms, how would you distinguish between the candidate genes to decide which is most likely to encode the CFTR gene?

Verified step by step guidance

1. Step 1: Understand the disease symptoms associated with cystic fibrosis, such as abnormal secretions in the lungs, pancreas, and sweat glands. These symptoms suggest that the CFTR gene is involved in processes related to ion transport and fluid balance.
2. Step 2: Analyze the functions of the three candidate genes within the 500-kb region on chromosome 7. Look for evidence that one of the genes is involved in ion transport, particularly chloride ion transport, as this is a hallmark of CFTR gene function.
3. Step 3: Examine the expression patterns of the candidate genes. The CFTR gene is expected to be expressed in tissues affected by cystic fibrosis, such as the lungs, pancreas, and sweat glands. Identify which gene has expression patterns matching these tissues.
4. Step 4: Investigate whether mutations in any of the candidate genes have been previously linked to cystic fibrosis symptoms. This can be done by reviewing genetic studies or databases that associate specific mutations with the disease.
5. Step 5: Perform functional studies, such as gene knockout or overexpression experiments, to determine which candidate gene's disruption leads to phenotypes resembling cystic fibrosis. This will help confirm the identity of the CFTR gene.

Key Concepts

Gene Function and Protein Encoding

Genes encode proteins that perform specific functions in the body. Understanding the role of the CFTR gene is crucial, as it encodes a protein that regulates chloride and bicarbonate ions across epithelial cell membranes. Mutations in this gene disrupt normal ion transport, leading to the symptoms of cystic fibrosis, such as thick mucus production and respiratory issues.

Mutation Types and Their Effects

Mutations can be classified into several types, including missense, nonsense, and frameshift mutations, each affecting protein function differently. Identifying the type of mutation in the candidate genes can help determine which gene is most likely responsible for cystic fibrosis. For instance, a nonsense mutation may lead to a nonfunctional protein, while a missense mutation might alter the protein's function.

Phenotypic Correlation

Phenotypic correlation involves linking genetic variations to observable traits or symptoms. In the context of cystic fibrosis, analyzing the symptoms and their severity can help identify which candidate gene is most likely the CFTR gene. By comparing the expression patterns and functional outcomes of the candidate genes with the known symptoms of cystic fibrosis, one can make an informed decision about the most likely gene involved.