Final answer:
In the scenario of a frameshift mutation at the 31st nucleotide base of a 90-nucleotide-long gene, the first 10 amino acids would remain unaffected. The subsequent amino acids would be altered due to the change in the reading frame caused by the mutation. This change could result in a nonfunctional protein.
Step-by-step explanation:
If a frameshift mutation occurs at the 31st nucleotide base of a gene that is 90 nucleotides long, the number of amino acids unaffected by this mutation can be determined by understanding the nature of codons and the impact of such mutations. Since each set of three nucleotides, known as a codon, encodes one amino acid, the first ten amino acids, which correspond to the first 30 nucleotides, will be unaffected because the mutation occurs after them. Therefore, 10 amino acids will be unaffected by the mutation.
However, after the 31st base, the frameshift would alter the reading frame and change every subsequent codon. Depending on the exact nature of the mutation, such as whether it results in an early stop codon or a change in every following amino acid, it could lead to a truncated or nonfunctional protein. It's important to note that a frameshift mutation caused by the insertion or deletion of nucleotides not in multiples of three is particularly problematic as it can lead to a significant alteration of the protein sequence from the mutation point forward, potentially rendering the protein nonfunctional.