A single base mutation in a gene may not ‘always’ result in loss or gain of function

A single base mutation in a gene may not ‘always’ result in loss or gain of function. Do you think the statement is correct? Define your answer.

The statement is correct. Because of degeneracy of codons, mutations at third base of codon usually do not result into any change in phenotype. On the other hand, if codon is changed in a way that now it specifies another amino acid it may alter the protein function as it happens in case of (1-globulin of haemoglobin protein, where a substitution of valine instead of glutamic acid causes change in its structure and function, and resulting into sickle-cell trait.