Genetic Code—Degeneracy and the Wobble Hypothesis In the standard genetic code, multiple codons can encode the same amino acid (degeneracy). Codons that specify the same amino acid differ predominantly at which position(s)?

Introduction / Context:
The genetic code is degenerate, meaning most amino acids are encoded by more than one codon. Francis Crick's wobble hypothesis explains why transfer RNA (tRNA) can recognize multiple codons through flexible pairing at one specific nucleotide position. This question asks you to identify where synonymous codons most commonly differ and how that relates to the wobble concept.

Given Data / Assumptions:

• A codon consists of three nucleotides written 5'→3'.
• Synonymous codons often vary at only one position.
• The tRNA anticodon pairs antiparallel to the mRNA codon, with the wobble at the 5' end of the anticodon (3' end of the codon).

Concept / Approach:
Because tRNA recognition tolerates non-canonical base pairing at the wobble site, most degeneracy is concentrated at the third base of the codon. Therefore, statements referring to the third base and to the wobble position are essentially describing the same phenomenon. Selecting the option that captures both ideas avoids any ambiguity in terminology.

Step-by-Step Solution:

Verification / Alternative check:
Survey of the code table shows many amino acids with quadruplet or doublet sets differing at base 3. Exceptions are limited (e.g., Met AUG and Trp UGG are single-codon amino acids).

Why Other Options Are Wrong:

• First base: changes here often switch to a different amino acid class and are less commonly synonymous.
• Second base: strongly influences amino acid chemical class; differences here usually are non-synonymous.
• Third base or wobble alone are individually true but the most complete answer acknowledges both labels.

Common Pitfalls:
Confusing the codon's third base (mRNA) with the anticodon's first base (tRNA). Remember codon position 3 pairs with the wobble site of the anticodon.

Final Answer:
Both (b) and (c)