Mutation year 2

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  • Created by: Hindleyc
  • Created on: 12-04-19 12:06
What does the ability of a cell to survive depend on
the instructions carried by the DNA
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If the DNA is damaged then what can't the cell do
make the correct proteins
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What have cells evolved
Many ways to make sure any damage to DNA is kept to a minimum
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What is the most dangerous time for DNA
When the cell is replicating
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What is the name of on the enzymes involved in controlling this process and what does it do
dna polymerase- proof reads the DNA copies to make sure all base pairing is corrrect eg if detects incorrect pairing will remove one and replace with correct base before moving on
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What can errors do, but
Sometimes slip through, most of them are recognised and repaired
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How do mutations occur
Spontaneously
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What are they
Changes in genes which are passed on to daughter cells
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How
DNA is a very stable molecule and doesn't suddenly change without reason but bases can change whenDNA is being replicated
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What is replication normally
extremely accurate - even error checking procedures in place to ensure accuracy but very occasionally mistakes do occur
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mutation=
base pairing error during DNA replication - unpredictable change in genetic material of the organism
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When can gene mutations happen
At any time but are most likely during DNA replication at interphase
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What is substitution
Type of gene mutation in which a nucleotide in a section of a DNA molecule is replaced by another nucleotide that has a different base
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3 possible consequences depend on
which new base is substituted for the original base
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What could be formed
1 of 3 stop codons that mark end of PP chain as a result production of the polypeptide coded for by the section of DNA would be stopped prematurely
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What would the final protein be
almost certainly significantly different and protein could not preform its normal function
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2nd consequence
Formation of a codon for a different AA meaning that structure of PP produced would differ in a single AA
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What if protein of which this PP is a part of do
May differ in shape and not function properly eg if enzyme AS no longer fits substrate won't catalyse reaction
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3rd consequence
Formation of a diff codon but one that produces a codon for the same AA as before- bc genetic code is degenerate and so most AA have more than 1 codon so mutation therefore has no effect on PP produced and so the mutation will have no effect
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What do some gene mutations change
only 1 triplet code due to the degerate nature of the genetic code, not all such mutations result in a change to encoded AA
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What is deletion
Loss of a nucleotide base from a DNA sequence may seem minor but impact on phenotype can be enormous
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What can 1 deleted base create
Frame shift because the reading frame that contains each 3 letters of the code has been shifted to left by 1 letter
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How is the gene now read
In the wrong 3 base groups and coded information is altered, most triplet will then be different as will the AA they code for
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So what will the PP be
Different and lead to the production of non-functional protein that could considerably alter phenotype
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What could one deleted base at the very start of the sequence do
Could alter every triplet in sequence
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What is addition
Extra bases becomes inserted in the sequence
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What does it usually have
a similar effect to a base deletion -usually frame shift and whole sequence of triplets becomes altered to the right
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What if 3 extra bases are added or any multiple of 3
there will be no frame shift so resulting PP will be different from 1 produced form a non-mutant gene but not to the same extent as there was a frame shift
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What do some gene mutations change
Natures of all base triplets downstream from the mutation ie result in frame shift often affects 3d structure of proteins and its function
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What is duplication of bases
One or more bases are repeated producing FS to right
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Inversion of bases
Groups of bases become separated from DNA sequence and rejoin at same position but in the inverse order (back to front) base seq of this portion is therefore reversed and effects the AA seq that results
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What is Translocation of bases
Groups of bases become separated from the DNA seq on one chromosome and become inserted into the DNA sequence of a different chromosome
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What does it often have
Significant effects on gene expression leading to an abnormal phenotype and these effect increase the development of certain forms of cancer and reduced fertility
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What can mutations in body cells not be
passed onto offspring because only mutations in sex cells can be passed on
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Why can an allele often not spread
because its effects are too damaging eg if protein coded for in original allele is vital and organism cannot produce it then organism will not develop
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How do gene mutations occur
naturally at random
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as we get older
more and more cells contain gene mutations
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What must all of the different alleles of a gene must once have been produced
by mutation
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If new allele codes for a useful protein what will it be
passed on (process of N selection)
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What do some gene mutations change
nature of all base triplets downstream from mutation (frame shift)
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What do some gene mutations change
1 triplet code due to degenerate nature of the genetic code not all mutations result in change to encoded AA
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wHEN may they arise
During DNA replication
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When do they occur
spontaneously
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What can they result in
different AA sequence in the encoded PP
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How is mutation rate increased
by mutagenic agents such as chemicals or radiation
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What do high energy ionising radiation and alpha etc radioactive solutes do
ionise bases therefore don't form correct base pairs- some viruses change base seq in DNA causing genetic disease and cancer
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What can chemicals do
Interfere with transcription
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Early earth
more mutagens contribute to greater diversity of life
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Cons of mutation
Almost always harmful and produce an organism that is less well suited to its environment, mutations that occur in body cells rather than in gametes lead to disruption of normal cellular activities such as cell division eg cancer
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Pros (benefits)
genetic diversity necessary for natural selection and speciation
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Other cards in this set

Card 2

Front

If the DNA is damaged then what can't the cell do

Back

make the correct proteins

Card 3

Front

What have cells evolved

Back

Preview of the front of card 3

Card 4

Front

What is the most dangerous time for DNA

Back

Preview of the front of card 4

Card 5

Front

What is the name of on the enzymes involved in controlling this process and what does it do

Back

Preview of the front of card 5
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