Transcript The Dna code - Winston Knoll Collegiate

THE DNA CODE
The Key to Protein Synthesis
The Question of DNA

DNA stores information to build proteins in
sequences of nucleotides
- DNA nucleotides contain one of 4 nitrogen
bases A T C G
- there are 20 different amino acids used to
build protein
Problem: How to code for 20 amino acids
with only 4 nitrogen bases?
Solution: Use groups of 3 nucleotides to code
for each amino acid
Why are 3 nucleotides required?
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Using one nucleotide can only code for 4
amino acids
Using pairs of nucleotides produces 16
combinations – can code for 16 amino acids
Using groups of three nucleotides produces
64 different combinations – can code for all
20 amino acids
- several different groups can each code
for the same amino acid
THE DNA CODE
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The DNA code is:
- universal to all living things
-the groups of nucleotides code for the
same amino acid in all living things
3 DNA nucleotides = Triplet
- one triplet = one amino acid
Examples – TCA = Serine
CTG = Aspartic Acid
THE CODE CONTINUED

3 mRNA nucleotides = Codon
- codon is the complement of a triplet
- codon codes for the same amino acid
as the triplet it is complementary to
Example:
DNA triplet = CTG = Aspartic Acid
mRNA codon = GAC = Aspartic Acid
Triplet
Codon
Transcription
Amino Acid
Translation
DNA
Triplet
mRNA
Codon
Amino
Acid
CTG
GAC
Aspartic
Acid
CGC
GCG
Alanine
THE CODON CHART – FROM CODON TO AMINO
ACID
Codon = UGC
Cysteine
Codon = CAC
Histidine
Codon = AAA
Lysine
Codon = GCG
Alanine