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


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