Stop codon nomenclature In classic genetic nomenclature, which termination codon is referred to as “amber”?

Introduction / Context:
Beyond their sequences, stop codons have historical names used in classic genetics literature and exam questions: amber, ochre, and opal (or umber). Remembering which name maps to which triplet helps in reading older papers and understanding mutant designations (e.g., amber suppressors).

Given Data / Assumptions:

• Standard genetic code terminology.
• Mapping codon triplets to historical names.
• Single-choice identification.

Concept / Approach:

The three termination codons are UAG (amber), UAA (ochre), and UGA (opal/umber). The “amber” designation originated from a researcher’s surname (H. J. Amber—apocryphal play on words), later complemented by ochre and opal for the other stops. These names persist in genetics contexts, especially suppressor tRNA studies.

Step-by-Step Solution:

Verification / Alternative check:

Standard codon tables and genetics glossaries consistently map UAG → amber; UAA → ochre; UGA → opal.

Why Other Options Are Wrong:

• UAA is ochre, not amber.
• UGA is opal (or umber), not amber.
• AUG is the start codon (Met), not a termination codon.
• UUA encodes leucine.

Common Pitfalls:

• Swapping ochre and amber; a mnemonic is “AmbEr = UAG (both contain A and G).”

Final Answer:

UAG (amber)