Decoding codons Which of the following codons encodes the amino acid serine (Ser) under the standard genetic code?

Introduction / Context:
Accurate decoding of codons is essential in genetics, cloning, and interpreting variants. Serine is encoded by six codons in the standard genetic code. This question tests recognition of one of those serine codons among distractors that encode other amino acids or serve different roles.

Given Data / Assumptions:

• Standard genetic code (not mitochondrial variants).
• Single-codon selection among multiple options.
• Focus on serine (Ser).

Concept / Approach:

Serine codons are UCU, UCC, UCA, UCG, AGU, and AGC. Among the given options, AGU matches serine. Other codons here specify arginine (CGA), histidine (CAU), methionine/start (AUG), or tryptophan (UGG).

Step-by-Step Solution:

Verification / Alternative check:

Consulting any codon table confirms AGU → Ser, while CGA → Arg, CAU → His, AUG → Met (start), UGG → Trp.

Why Other Options Are Wrong:

• CGA: Arginine.
• CAU: Histidine.
• AUG: Methionine and start signal.
• UGG: Tryptophan.

Common Pitfalls:

• Mistaking AGG (Arg) or AGC (Ser) for AGU; only AGU among provided choices encodes Ser.

Final Answer:

AGU