Describe the redundancy of the genetic code and identify the start codon.

• A. Redundancy means multiple codons encode different amino acids; start codon is AUG; there are 64 codons total.
• B. Redundancy means that each amino acid is coded by a single codon; start codon is AUG; there are 61 codons.
• C. There are 64 codons total, all of which encode amino acids.
• D. There are 64 codons total with 61 coding for amino acids and 3 stop signals; start codon is AUG.

Answer: (D)

Redundancy means that most amino acids are specified by more than one codon, a feature called degeneracy. There are 64 possible codons in the genetic code, but only 61 encode amino acids while 3 are stop signals that terminate translation. The start codon is AUG, which initiates translation and also codes for methionine as the first amino acid in many organisms. This combination—64 total codons, 61 for amino acids, 3 stops, and AUG as the start codon—best reflects how the code is organized.