Evaluating Genetic Statements on Coding and Mutations

Steps:

• Statement 1: Peptides consist of amino acids encoded by mRNA from genes, so all are gene-coded.
• Statement 2: Proteins form from amino acid sequences via translation, not directly from genes.
• Statement 3: Gene mutations are defined as changes in DNA nucleotide sequences.
• Statement 4: Some mutations, like silent ones, do not alter the polypeptide due to codon degeneracy.

Why B is correct:

• B selects statements 1 and 3, aligning with central dogma of molecular biology where genes code peptides and mutations change nucleotide sequences.

Why the others are wrong:

• A includes false statements 2 and 4.
• C includes false statement 2.
• D lists only 1 and 3 but omits "only," potentially implying others; however, B precisely matches correct pair.

Final answer: B