Mutation

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  • Created by: Hindleyc
  • Created on: 23-06-18 14:45
What do gene mutations involve?
Change in the base sequence of chromosomes
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How can they arise?
Spontaneously during DNA replication and include base deletions and substitution
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Why don't all base substitutions cause a change in the sequence of the encoded AA?
Due to the degenerate nature of the genetic code
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What can increase the rate of gene mutation?
Mutagenic agents
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What does the ability of a cell to survive depend on?
the instructions carried by the DNA
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What happens if DNA is damaged?
Cells cannot make correct proteins
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What have cells therefore evolved?
Many ways to make sure any damage to DNA is kept to a minimum
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What the most dangerous time for DNA?
When the cell is replication
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What are mutations?
Changes in genes which are passed onto daughter cells
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When can bases change ? what is replication normally?
When DNA is being replicated - normally replication is extremely accurate as error-checking precautions in place but occasionally mistakes occur
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So a mutation is
Base-pairing error during DNA replication at interphase
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What is a mutation
Unpredictable change in genetic material of an organism
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How many they occur? How is rate of mutation increased- what does this do? what is this serious in? what can some viruses do? As they were more mutagens in early history what does this mean?
Spontaneously. By chemicals/ radiation (mutagens- mutagenic agents).EG x-rays ionise bases so they don't form correct base pairs. Serious in tissues where cell division occurs- rapid. Some V can change base SEQ. More M so more diversity
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What is an addition mutation?
An extra nucleotide inserted so an extra base Is added to the sequence
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What is a deletion mutation?
A nucleotide is removed
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What is a substitution mutation?
A nucleotide is replaced with one with a different base
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What are other types
Inversion of a sequence of bases, or duplication of bases
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What can't mutation is body cells be passed on to?
offspring as only mutation in sex cells
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Why can the allele often not spread
Because effects are too damaging eg if P coded for in original allele is vital and organism can't produce it then O won't develop
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How do gene mutations occur naturally?
At random
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What happens as we get older?
More and more cells contain gene mutations
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What does the effect of a gene mutation depend on?
How much code is disrupted
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What does a single substitution do?
Affect one codon so may not have any/much effect
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What do an addition or deletion do?
May affect all codons beyond error and so may affect sequence of AA in protein being coded for
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What is this known as?
Frame shift that often affects 3D structure of protein and its function
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What must all of the different alleles of a gene must once have been produced by?
A mutation
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What happens in new allele codes for a useful protein?
It will be passed on- if it is harmful it is unlikely to be passed on
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What does a substitution mutation affect
1 AA so tends to have less severe effects
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What if sub is on 3rd base of codon?
May have no effect at all because 3rd base often doesn't affect AA being coded for (eg all bases beginning with CC code for Proline)
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What is this known as?
Silent mutation
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What if a mutation leads to a premature stop codon?
Protein will be incomplete and certainly non-functional
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What is this known as?
Non-sense mutation
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What is a Misense mutation?
Mutation change code for 1 AA so 1 AA in SEQ changes
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what do deletion and insertion mutation have?
More serious effects as they are Fram shift mutations- change codons reading frame even though they don't change actual sequence of bases
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What happens to all AA downstream of mutation
Wrong and protein completely wrong and non-functional
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How can the effect of a deletion be cancelled out by?
A near by insertion or 2 more deletions because this will restore reading frame (similar for substitution)
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Other cards in this set

Card 2

Front

How can they arise?

Back

Spontaneously during DNA replication and include base deletions and substitution

Card 3

Front

Why don't all base substitutions cause a change in the sequence of the encoded AA?

Back

Preview of the front of card 3

Card 4

Front

What can increase the rate of gene mutation?

Back

Preview of the front of card 4

Card 5

Front

What does the ability of a cell to survive depend on?

Back

Preview of the front of card 5
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