Final answer:
A frameshift mutation, caused by the insertion or deletion of nucleotides, results in a string of altered amino acids at the end of a polypeptide product and can lead to non-functional or truncated proteins.
Step-by-step explanation:
The type of mutation that results in a string of altered amino acids at the end of the polypeptide product is a frameshift mutation. Frameshift mutations occur due to the insertion or deletion of one or more nucleotides in the DNA sequence. Unlike a silent mutation, which does not alter the amino acid sequence of a protein, a frameshift mutation changes the reading frame resulting in a completely different sequence of amino acids from the point of mutation onward. This can lead to the production of non-functional proteins or truncated proteins if the shift introduces a premature stop codon.