Download 8.2 Triplet code

8.2 Triplet code
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Learning objectives
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Define the term gene
Explain how genes codes for
polypeptides
A gene is…
A gene is….
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Section of DNA with a sequence of
DNA bases that determines the
sequence of amino acids in a
polypeptide , hence the structure of
the protein
How?
Triplet code
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One gene = one
polypeptide.
A gene is length of
nucleotide bases.
Every 3 bases is
called a triplet.
Each triplet codes
for an amino acid
The DNA code
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It is read in triplets of nucleotide bases
It has 4 different letters (bases) ACTG
43 gives 64 different codes for the 20 amino acids.
Introns DNA that does not code for amino acids
It is non overlapping 123456= 123 456
It is degenerate (most amino acids more than one
triplet code)
Start codon is always the same.
3 different STOP codons.
Universal code same in all organisms
Proteins
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Why is the order
of the amino
acids important in
a protein?
What is different
about these
proteins? Why
does it matter?
What do the
alternative codons per
amino acid have in
common?
Working out the code
ATCCGTAACGTAACGGTA
What would the complementary bases
be?
Including a start and stop codon how
many amino acids would be produced?