Genetic Code Table

Explore the standard genetic code: interactive table of 64 codons, each linked to its amino acid. Click any codon or type a triplet to instantly retrieve full name, three‑letter and one‑letter codes.

Accepts RNA bases (A, U, G, C) or DNA (T automatically converted to U). Case insensitive.
? Start: AUG (Met)
? Stop: UAA (Ochre)
? Stop: UGA (Opal)
? CCG → Proline
⭐ Tryptophan (UGG)
? Lysine (AAG)
1st baseU (2nd)C (2nd)A (2nd)G (2nd)
Start (AUG) Stop (UAA, UAG, UGA) Click any cell → auto‑fill lookup
Privacy first: All codon translations are performed locally. No data leaves your browser.

The Standard Genetic Code: Deciphering Life’s Blueprint

The genetic code is a set of rules by which information encoded in genetic material (DNA or RNA sequences) is translated into proteins by living cells. It defines how sequences of nucleotide triplets, called codons, specify which amino acid will be added next during protein synthesis. The code is nearly universal, shared by almost all organisms, from bacteria to humans – a testament to a common evolutionary origin.

? 64 codons → 20 standard amino acids + 3 stop signals. Degenerate (redundant) yet unambiguous.

History & Scientific Milestones

In the early 1960s, Marshall Nirenberg, Heinrich Matthaei, and Har Gobind Khorana cracked the genetic code using cell‑free systems and synthetic RNA homopolymers. Nirenberg and Matthaei discovered that the codon UUU codes for phenylalanine, initiating the race to decode all 64 triplets. By 1966, the entire code had been elucidated. This breakthrough earned them the 1968 Nobel Prize in Physiology or Medicine. The standard genetic code table shown here (RNA version) remains a cornerstone of molecular biology, bioinformatics, and genetic engineering.

Key Properties of the Genetic Code

  • Triplet nature: Three nucleotides per codon (4³ = 64 possible combinations).
  • Degeneracy / redundancy: Most amino acids are encoded by more than one codon (e.g., Leucine has 6 codons). This buffers against mutations.
  • Unambiguous: Each codon specifies only one amino acid (or termination).
  • Non‑overlapping & comma‑less: Codons are read sequentially without gaps or overlaps.
  • Start & stop signals: AUG (Methionine) initiates translation; UAA, UAG, UGA terminate protein synthesis.
  • Near‑universality: Mitochondrial and some protozoan variants exist, but the nuclear code is highly conserved.

How to Use This Interactive Genetic Code Table

  1. Click any codon cell in the table below – it will automatically populate the search box and show the corresponding amino acid details.
  2. Type a codon (e.g., “AUG”, “UCC”, or “TAA” for DNA mode) into the input field and press “Translate”. DNA thymine (T) is automatically converted to uracil (U).
  3. Instant results display the full amino acid name, three‑letter abbreviation, one‑letter symbol, and special notes (start/stop).
  4. Use preset examples to quickly explore start codons, stop codons, or rare amino acids like tryptophan.

Amino Acid Nomenclature & Codon Distribution

Amino Acid Three‑letter One‑letter Codons (RNA) Frequency / role
Methionine Met M AUG Start, essential
Tryptophan Trp W UGG Largest, rare
Leucine Leu L UUA, UUG, CUU, CUC, CUA, CUG Most abundant in proteins
Serine Ser S UCU, UCC, UCA, UCG, AGU, AGC Polar, phosphorylatable
Arginine Arg R CGU, CGC, CGA, CGG, AGA, AGG Basic, DNA‑binding
Stop Ter (Stop) * UAA, UAG, UGA Termination signals
Case Study: Synonymous Mutations & Codon Bias

Due to the degeneracy of the genetic code, some mutations (synonymous) do not change the encoded amino acid. However, organisms exhibit codon usage bias — preferential use of specific synonymous codons. For example, E. coli favors certain codons for highly expressed genes, impacting heterologous protein expression. Synthetic biologists leverage codon optimization to maximize protein yield. This interactive table helps visualize which synonymous codons correspond to each amino acid, a vital resource for gene design and molecular cloning.

Beyond the Standard Code: Natural Variations

While the table above represents the standard nuclear genetic code, exceptions exist. Vertebrate mitochondria use AUA for methionine instead of isoleucine, and AGA/AGG as stop codons instead of arginine. Some protozoans (e.g., Euplotes) reassign UAA and UAG to glutamine. Such deviations highlight the evolutionary plasticity of the genetic code, but the standard code remains the reference for most genetics education and genome annotation.

Frequently Asked Questions (FAQ)

Degeneracy means most amino acids are encoded by more than one codon. This reduces the deleterious effects of mutations because a single nucleotide change may still code for the same amino acid (synonymous substitution).

RNA uses Uracil (U) while DNA uses Thymine (T). The table shown is for mRNA codons (RNA). For DNA, replace T with U (e.g., DNA codon ATG corresponds to RNA AUG → Methionine). Our tool automatically converts T to U.

No, the genetic code is unambiguous. Each codon specifies only one amino acid (or stop). However, in rare cases, recoding events (e.g., selenocysteine incorporation with UGA) occur, but they require special regulatory elements.

AUG codes for methionine in eukaryotes (and formylmethionine in bacteria). The start signal context (Kozak or Shine‑Dalgarno) defines translation initiation, but the codon itself remains methionine.

Absolutely. Enter a DNA triplet (e.g., ATG, TAA) and the tool will replace T with U and return the correct amino acid. Perfect for reverse‑complement analysis or ORF prediction.

Check public databases such as Kazusa Codon Usage Database, NCBI, or GenBank for species‑specific codon frequency tables.

Scientific accuracy & expert background – This genetic code tool follows the official IUPAC standard translation table 1 (nuclear code). Verified against NCBI’s genetic code reference and classic molecular biology texts (Alberts’ Molecular Biology of the Cell, Lehninger Principles of Biochemistry). Updated April 2026 by the GetZenQuery Tech team, in collaboration with academic consultants.

Primary references: NCBI Genetic Code Tables, Nirenberg, M. et al. (1965) “RNA codewords and protein synthesis”, UniProt Genetic Code.