Question

a dna mutation results in a protein that is the same as the initial protein synthesized before the mutation. which statement best explains this outcome?
a one amino acid substitution does not affect protein synthesis.
b different codons can be translated into the same amino acid, so some mutations do not affect protein synthesis.
c only mutations that occur at the chromosomal level change protein function.
d amino acids have similar functions, so their corresponding proteins are unaffected by mutations.

Explanation:

• Option A: A single amino - acid substitution can affect protein synthesis. For example, in sickle - cell anemia, a single amino - acid substitution (valine instead of glutamic acid) in the hemoglobin protein causes a significant change in the protein's function and structure. So, this option is incorrect.
• Option B: The genetic code is degenerate. That is, different codons (triplets of nucleotides in mRNA) can code for the same amino acid. For example, the codons GGU, GGC, GGA, and GGG all code for the amino acid glycine. So, if a DNA mutation results in a codon change that still codes for the same amino acid, the protein synthesized will be the same as the original. This option is correct.
• Option C: Mutations at the gene level (not just chromosomal level) can change protein function. For example, point mutations (a type of gene - level mutation) can lead to non - functional proteins. So, this option is incorrect.
• Option D: Amino acids have distinct functions. For example, hydrophobic amino acids (like phenylalanine) and hydrophilic amino acids (like serine) have different chemical properties that affect protein folding and function. Mutations that change amino acids can (and often do) affect protein structure and function. So, this option is incorrect.

Answer:

B. Different codons can be translated into the same amino acid, so some mutations do not affect protein synthesis.