Final answer:
A mutation in the CFTR gene can have varying effects, but in relation to cystic fibrosis, it is likely to be deleterious. Natural selection will act on the mutation based on whether it is neutral, beneficial, or deleterious, with most CFTR mutations leading to negative outcomes such as impaired lung function.
Step-by-step explanation:
If there is a mutation in the human CFTR gene that results in an altered amino acid at a specific position, the effects can range from neutral, beneficial, or deleterious. However, in the case of the CFTR gene which is associated with cystic fibrosis (CF), most mutations are likely to be deleterious because the CFTR protein plays a crucial role in transporting chloride ions across cell membranes. If the protein's function is impaired, it can lead to the accumulation of thick mucus in various organs, particularly the lungs.
Natural selection will act on this mutation depending on its effect on the organism's fitness. A deleterious mutation would likely be selected against because individuals carrying it would have reduced fitness. For example, those with two copies of the mutant gene may develop CF and potentially have reduced reproductive success. On the other hand, a benign mutation would not affect the individual's fitness and would be neither selected for nor against. A beneficial mutation could be selected for if it confers a survival or reproductive advantage, as seen with heterozygote carriers for CFTR mutations, who might have increased resistance to certain infectious diseases.
However, the most common mutations in CFTR found in patients with cystic fibrosis are deleterious, leading to the malfunction of the CFTR protein. Therefore, a prediction can be made that a random mutation at position 'A' is more likely to be deleterious rather than neutral or beneficial.