When a base is substituted but the triplet code still codes for the same amino acid
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How can a different triplet code still code for the same amino acid?
Degenerate code- more than one triplet code codes for a single amino acid
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How does a silent mutation affect the polypeptide chain formed?
It doesn't - as the mutation still codes for the original sequence of amino acids, there will be no change in the polypeptide chain formed
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What is a nonsense mutation?
Where the mutation results in the formation of one of the three stop codons
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What are the 3 stop codons in DNA?
TAG, TAA and TGA
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How does this lead to the formation of a non-functional polypeptide chain?
The production of the polypeptide chain stops prematurely
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What is a mis-sense mutation?
It is a base change that results in a different amino acid being created.
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How does this lead to the formation of a non-functional polypeptide chain?
Different sequence of amino acids so the tertiary structure of the polypeptide chain will have changed, making it no longer functional
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What is a deletion mutation?
When a nucleotide is lost from the DNA sequence
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What effect does this cause?
A frame shift
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Explain what is meant by a frame shift and what it does
Bases are read as triplet codes rather than individually so when a base is deleted frame shift happens so the triplet codes change, leading to a different sequence of amino acids
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When does a frame shift have the largest effect?
When it happens at the start of a sequence
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What do proto-oncogenes do?
Stimulate cell division
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What can they mutate to?
Oncogenes
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What do oncogenes do?
They cause cell division in the absence of a growth factor by permanently activating a receptor protein and produce a growth factor in excessive amounts
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What do tumour suppressor genes do?
Slow down cell division
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Other cards in this set
Card 2
Front
How can a different triplet code still code for the same amino acid?
Back
Degenerate code- more than one triplet code codes for a single amino acid
Card 3
Front
How does a silent mutation affect the polypeptide chain formed?
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