Answer:
A buildup of sticky mucus on the outside of the cell
Step-by-step explanation:
The deletion of the codon means that the protein the gene codes for is missing one amino acid.
That protein acts as a Cl⁻ channel in the cellular membrane and controls the movement of water in the tissues.
The water produces thin, freely flowing mucus. Without the water, a coating of thick mucus builds up on the outside of the cell.