A mutation in either the DNA or the RNA could result in:
1. The wrong amino acid in protein - which may or not be important for proper functioning of the protein
2. If the mutation results in an internal stop codon instead of a normal coding codon then you could get a shortened polypeptide (so no protein made)
3. You could get a frameshift - if you lost one or more nucleotides - such that you end up with an entirely different amino acid sequence and thus potentially a nonsense protein
