Question

mutations in dna can have different effects on an organism’s phenotype. which of the following best explains why some mutations do not result in a phenotypic change?
all mutations change the amino acid sequence, but the cell repairs them before proteins are made.
mutations always lead to harmful changes in protein structure, which the organism compensates for by producing extra proteins.
some mutations occur in non - coding regions or result in a codon that codes for the same amino acid, leaving the protein unchanged.
mutations only affect rna molecules and never influence protein synthesis.

Explanation:

• Analyze Option 1: Not all mutations change amino acid sequences (e.g., silent mutations), and the claim about all mutations being repaired is incorrect.
• Analyze Option 2: Mutations don't always lead to harmful changes (some are neutral or beneficial), and the "extra proteins" explanation is wrong.
• Analyze Option 3: Mutations in non - coding regions don't affect protein coding. Also, due to the redundancy of the genetic code, some codon changes (silent mutations) code for the same amino acid, so the protein remains unchanged, leading to no phenotypic change. This matches the concept of why some mutations don't change the phenotype.
• Analyze Option 4: Mutations in DNA can affect RNA and protein synthesis, so this statement is false.

Answer:

C. Some mutations occur in non - coding regions or result in a codon that codes for the same amino acid, leaving the protein unchanged.