Codon Chart Activity
Goal: Read the genetic code from a codon chart, find every codon for an amino acid, and explain why 64 codons code for only 20 amino acids.
What to do
- For each codon in the table, find its first base in the left column, its second base in the next column and its third base along the top of the chart. Record the amino acid’s three-letter and one-letter codes.
- Type Leu into Find a codon or an amino acid and count how many cells light up. Then try Met, Trp and stop.
- Use the chart to answer the translation questions, stopping at the first stop codon.
Record your results
| mRNA codon | Amino acid (three-letter) | One-letter code |
|---|---|---|
| UGG | ||
| AUG | ||
| GCA | ||
| UUC | ||
| CCU | ||
| GAA | ||
| UAG |
Questions
How many codons code for leucine (Leu)? How many code for methionine (Met) and for tryptophan (Trp)?
Translate the mRNA 5′-AUG GCA UUC UAG-3′ into amino acids.
There are 64 codons but only 20 amino acids. How many codons code for amino acids, and what do the others do?
Which three amino acids have six codons each?
A DNA template strand reads 3′-TAC-5′. Which mRNA codon and amino acid does it give, and why must you transcribe it before using the chart?
Challenge: a mutation changes the codon UGG to UGA. What happens to the protein?
Free from Biology Lab · thebiologylab.org · HS-LS1-1: Explain how the structure of DNA determines the structure of proteins, which carry out the essential functions of life.