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What are mutations?
Changes to the sequence of bases in a gene that can occur during DNA replication
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What effects can mutations have on the genetic code?
- The mRNA codons produced are altered
- A different tRNA anticodon will bind to the codon
- A different amino acid will be added to the protein, changing its primary structure
- The protein will fold differently in its tertiary structure
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How does a substitution mutation occur?
One base is substituted for another
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What effects does a substitution mutation have?
- Only one triplet of bases is altered so only a single amino acid is different
- Due to the degenerative nature of the genetic code, some substitution mutations do not affect the primary sequence of the protein
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How does a deletion mutation occur?
a base is removed from the sequence
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What effects does a deletion mutation have?
- A frame shift occurs with new triplets formed
- Every triplet after the mutation is different so different amino acids are produced
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What can mutations produce?
New alleles
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What increases the frequency of mutations?
Mutagenic agents such as high energy radiation or chemicals (benzene)
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What is the function of pro-oncogenes?
To stimulate cell division in a healthy cell
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When should cells divide?
When they are required to during periods of growth and repair
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How is cell division stimulated?
- Growth factors bind to the surface protein receptors which become activated
- This causes relay proteins to switch on genes needed for cell division
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What can mutated pro-oncogenes become
- Oncogenes
- These are capable of causing cancer by stimulating uncontrollable cell division
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How might an oncogene cause cancer?
- It may produce a receptor protein that is permanently activated
- It might produce excessive amounts of growth factor
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What is the function of tumour suppressing genes?
To inhibit cell division when it is not needed
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How can tumour suppressing genes cause cancer?
If they become mutated and produce inactive proteins, failing to inhibit cell division
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