How to read a codon chart?

Sourav PanDecember 1, 2024

Answered

To effectively read a codon chart, follow these structured steps:

Understanding the Codon Chart

A codon chart is a reference tool that correlates sequences of three nucleotides (codons) in mRNA with their corresponding amino acids. The genetic code is universal, meaning it applies to nearly all organisms.

Components of the Codon Chart

1. Codons: Each codon consists of three nucleotides. There are 64 possible codons, which include:
   • 61 codons that encode for 20 different amino acids.
   • 3 stop codons that signal the termination of protein synthesis.
2. Amino Acids: Each amino acid can be specified by multiple codons, indicating that the genetic code is redundant. For example, proline can be coded by CCU, CCC, CCA, and CCG.

Structure of the Chart

• Rows and Columns:
  • The left column represents the first nucleotide of the codon.
  • The top row represents the second nucleotide.
  • The right column indicates the third nucleotide.

Steps to Read a Codon Chart

1. Identify Your Codon: Determine the mRNA codon you want to translate. For example, if your codon is AUG:
   • First base: A
   • Second base: U
   • Third base: G
2. Locate the First Base: Find the row corresponding to the first base (A) on the left side of the chart.
3. Find the Second Base: Move across to find the column for the second base (U) at the top of the chart.
4. Narrow Down to the Box: This will lead you to a specific box that contains four possible codons.
5. Identify the Third Base: Look at the right side of this box to find where your third base (G) fits in, which will pinpoint your exact codon within that box.
6. Read the Resulting Amino Acid: The intersection will reveal which amino acid is encoded by your specific codon. For AUG, this corresponds to methionine, which is also a start codon for protein synthesis.

Example

• For the codon CCA:
  • First base: C
  • Second base: C
  • Third base: A
  • Following steps will show that CCA codes for proline.

Additional Notes

• Start and Stop Codons:
  • The most common start codon is AUG (methionine).
  • Stop codons (UAA, UAG, UGA) do not code for any amino acids and signal termination of translation.
• Circular vs Rectangular Charts: Codon charts can be represented in different formats; both provide similar information but may be easier to read depending on personal preference.

By following these steps and understanding the structure of a codon chart, you can accurately translate mRNA sequences into their corresponding amino acids.

Amino Acids Codon Chart – Codon Table, mRNA Codon Chart