Universal Genetic Code

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Universal Genetic Code

• SC.912.L.16.9

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Evolution of the genetic code

• Genetic code
• four different bases combined in sequences of
  three yields 64 possible codons that code for the
  20 amino acids
• 61 code for amino acids, 3 code as stop or
  terminator
• codons that will signal the cell to stop protein
  synthesis
• each codon codes for a specific amino acid and
  some amino acids are coded for by more than one
  codon
• UNIVERSALsame in all organisms

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Evolution of the genetic code

• The modern genetic code
• must have evolved from a more primitive one
• Features characterizing the present one
• mRNA consists of 4 kinds of nucleic bases
• mRNA is coded as triplets

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Evolution of the genetic code
Features characterizing the present genetic
code 3) Code is commaless and
non-overlapping 4) Reading frame beginning
codon (AUG) stop codons (UAA, UAG, UGA) 5)
Triplets compliment tRNA anticodons
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Evolution of the genetic code
Features characterizing the present genetic
code 6) Code redundancy mostly in the third
codon position 7) More than one codon
designates each amino acid (quartets and
duets) 8) The universal code
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Evolution of the genetic code
The universal genetic code (and its exceptions)
The genetic code is the same in all organisms,
with only a few exceptions, because of a common
ancestor carrying the same genetic code
Mitochondria