In the genetic code, how many different codons specify (code for) a single amino acid?

• A. Exactly 1 codon
• B. Exactly 3 codons
• C. Exactly 64 codons
• D. Between 1 and 6 codons, depending on the amino acid

Answer: (D)

Verified step by step guidance

1. Understand that a codon is a sequence of three nucleotides in mRNA that corresponds to a specific amino acid or a stop signal during protein synthesis.
2. Recall that the genetic code is degenerate, meaning that most amino acids are encoded by more than one codon, but never more than six.
3. Recognize that there are 64 possible codons in total (4 nucleotides ^ 3 positions = 64), but these codons do not all code for different amino acids; some code for the same amino acid.
4. Note that some amino acids are specified by only one codon (e.g., methionine and tryptophan), while others can be specified by up to six different codons.
5. Conclude that the number of codons specifying a single amino acid ranges from 1 to 6, depending on the amino acid, which explains the correct answer.