GENETIC Code

Key Notes

What You Will Learn

• Definition of the genetic code

• How the genetic code is read

• Characteristics of the genetic code

What is the Genetic Code?

• The genetic code is the sequence of nitrogen bases (A, C, G, U) in mRNA

• Bases are grouped into triplets called codons

• Each codon codes for one amino acid or a start/stop signal

• There are 64 codons but only 20 amino acids

How is the Genetic Code Read?

• Translation begins at the start codon (AUG), which codes for methionine

• The mRNA sequence is read in groups of three bases (codons)

• Translation stops when a stop codon (UAG, UGA, or UAA) is reached

Characteristics of the Genetic Code

• Universal – Used by all known living organisms

• Unambiguous – Each codon codes for only one amino acid

• Redundant – Most amino acids have multiple codons

Summary

• The genetic code is based on the sequence of bases in DNA or RNA

• Codons (triplets of bases) code for specific amino acids

• The code is read in order from the start codon to a stop codon

• It is universal, unambiguous, and redundant