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What is a gene?

Features of the code:

A gene is a section of DNA that contains the coded information for
making polypeptides and functional RNA
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The remaining amino acids are coded for by between 2
and 6 triplets each
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A triplet is always read in one particular direction along
the DNA strand
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This codes for the amino acid
methionine
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Three triplets do not code for any amino acid
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The code is ‘non-overlapping’ = each base in the sequence
is only read once
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The code is ‘universal’, with a few minor exceptions, each
triplet codes for the same amino acid in all organisms
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The coded info is in the form a specific sequence of bases along the
DNA molecule
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(enzymes are proteins) as enzymes control chemical reactions they are responsible for an organisms development and activities
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A gene is a section of DNA located at a particular position, called a locus on a DNA molecule
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Their reasoning was:
1
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Each amino acid must have its own code of bases on the DNA

3
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If each base coded for a different amino acid, only four different amino acids
could be coded for

5
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Three bases produces 64 different codes, more than enough to satisfy the requirements of 20 different amino acids
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Much of the DNA in eukaryotes doesn't code for polypeptides
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Even within
genes, only certain sequences code for amino acids
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Within the gene these exons
are separated by further non-coding sequences called INTRONS

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