Any change in the to the quantity or structure of the DNA of an organism
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What is a gene mutation?
Any change to one or more nucleotide bases or any rearrangement of the bases
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What are the six different types of gene mutation?
Substitution of bases, deletion of bases, addition of bases, duplication of bases, inversion of bases, translocation of bases
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What is a substitution mutation?
When a nucelotide in a section of DNA molecule is replaced by another nucleotide that has a different base
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What are the three possible consequences of a substitution mutation?
- Formation of a stop codon - Formation of a codon for another amino acid - Formation of a codon that is different but codes for the same amino acid
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What is a deletion substitution?
When there is a loss of a nucelotide base from a DNA sequence
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What is the name of the effect caused by a deletion mutation?
Frame-shift
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In which direction is the frame-shift in a deletion mutation?
to the left
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What happens when a frame-shift occurs in a deletion mutation? What is the impact on the resulting polypeptide?
Each base triplet after the deletion of the base is read differently and the resulting polypeptide will generally be non-functional, the impact on the phenotype depends on the location of the deletion along the gene
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Where along the gene would a deletion mutation be least impactful?
At the end of the gene as less of the sequence is disrupted
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What is an addition mutation and what effect does it have on the DNA sequence?
It is when an extra base is inserted into the sequence, causing a frame-shift to the right
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When would an addition mutation not cause a frame-shift?
If three bases or any multiple of three bases were added at a time
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What is the duplication of bases mutation and what effect does it have on the DNA sequence?
When one or more bases are repeated, which causes a frame-shift to the right
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What happens during an inversion of bases mutation?
A group of bases become separated from the DNA sequence and rejoin at the same point but in the inverse order
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What is a translocation of bases mutation?
When a group of bases become separated from the DNA sequence and become inserted into the DNA sequence of a different chromosome
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What effect can a translocation mutation have on an individual?
Significant effects on gene expression- leading to abnormal phenotype which can be the development of certain forms of cancer and reduced fertility
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What do mutagenic agents do?
They increase the rate at which a mutation can occur
It can convert cytosine in DNA to uracil by removing an -NH2 group
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How does benzopyrene act as a mutagenic agent?
By adding a large group to guanine it can prevent it from pairing with cytosine. When DNA polymerase reaches the affected guanine it inserts any other base available in the TP53 tumour suppressor gene (inactivating it)
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Where is benzopyrene found?
In tobacco smoke
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How does ionising radiation act as a mutagenic agent?
It produces free radicals in cells which alter the shape of bases in DNA so that DNA polymerase can no longer act on them
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How does UV act as a mutagenic agent?
It causes thymine in DNA to form bonds with the nucleotides on either side of it which disrupt DNA replication
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Other cards in this set
Card 2
Front
What is a gene mutation?
Back
Any change to one or more nucleotide bases or any rearrangement of the bases
Card 3
Front
What are the six different types of gene mutation?
Back
Card 4
Front
What is a substitution mutation?
Back
Card 5
Front
What are the three possible consequences of a substitution mutation?
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