AUG Codon: Dual Role & Start Signal — NEET Biology
✅ Asked in NEET 2021AUG has dual functions. It codes for Methionine (met), and it also act as initiator codon.
AUG codes for methionine and uniquely acts as the start/initiator codon in protein synthesis. Students often mistakenly believe AUG only codes for methionine or forget its initiator function—these are actually two separate roles. The key difference: when AUG appears at the beginning of mRNA (5' end near ribosome binding site), it signals translation start and codes for N-formylmethionine in prokaryotes or regular methionine in eukaryotes; when AUG appears internally, it codes only for methionine. Remember: first AUG = start signal + methionine; internal AUG = just methionine. This dual function appears frequently in NEET because it tests both genetic code knowledge and translation mechanics.
This paragraph was tested 2 times in NEET.
Statement I: Codon ‘AUG’ codes for methionine and phenylalanine. Statement II: ‘AAA’ and ‘AAG’ both code for lysine. (NEET 2021)
Starter codon is: (NEET 2016 Phase 1)
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