A change in a single nucleotide will not always result in a changed protein. It may or may not produce a changed protein which depends on the substituted nucleotide. This can be better explained using the different amino acid codons.
We know that proteins are made up of amino acids ; the basic structure and properties of a particular protein changes with a change in its constituent amino acids. Proteins are formed as a result of translation process ...
This solution explains whether a change in a single DNA nucleotide always results in a changed protein or not. It has been described with detailed examples. It is a single page PDF document with original contents.