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What are mutations?
Changes to the sequence of bases in a gene that can occur during DNA replication
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
How does a substitution mutation occur?
One base is substituted for another
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
How does a deletion mutation occur?
a base is removed from the sequence
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
What can mutations produce?
What increases the frequency of mutations?
Mutagenic agents such as high energy radiation or chemicals (benzene)
What is the function of pro-oncogenes?
To stimulate cell division in a healthy cell
When should cells divide?
When they are required to during periods of growth and repair
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
What can mutated pro-oncogenes become
- These are capable of causing cancer by stimulating uncontrollable cell division
How might an oncogene cause cancer?
- It may produce a receptor protein that is permanently activated
- It might produce excessive amounts of growth factor
What is the function of tumour suppressing genes?
To inhibit cell division when it is not needed
How can tumour suppressing genes cause cancer?
If they become mutated and produce inactive proteins, failing to inhibit cell division
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