Which of the following is a correct difference between the start and stop codons in a final mRNA sequence that leaves the nucleus? Select one: a. The start codon does not code for an amino acid but the stop codon does code for an amino acid. b. There are multiple possible sequences for start codons but there is only one possible sequence for a stop codon c. Mutations corresponding with the start codon impact protein function, but mutations in the stop codon do not impact protein function. d. The start codon is always the very first letter of the final mRNA sequence, and the stop codon is always the last letter of the final mRNA sequence. e. All of the choices are correct differences between the start and stop codons in an mRNA sequence. f. None of the choices are correct differences between the start and stop codons in an mRNA sequence.