8 The Control of Gene Expression- Mutation Flashcards
What are mutations and what are they caused by?
-Changes in the base sequence of DNA
-Caused by errors in DNA replication
What is an addition mutation?
-Where one or more bases are added to the DNA sequence
-Eg ATCGTT—> ATCCGTT
What is a deletion mutation?
-Where one or more bases are removed from DNA sequence
-Eg ATCGTT—> ATCTT
What is a substitution mutation?
-Where one or more bases are changed in DNA sequence
-Eg ATCGTT—> ACCGTT
What is an inversion mutation?
-Where one or more bases in DNA sequence are inverted (reversed)
-Eg ATCGTT—> TTGCTA
What is a duplication mutation?
-Where one or more bases are duplicated (repeated) in DNA sequence
-Eg ATCGTT—> ATATCGTT
What is a translocation mutation and where is this found?
-Where a section of DNA sequence is moved to another section of DNA sequence
-Can be within & across chromosomes
What doe a mutation do to protein structure and what is the effect of this?
-Give rise to change in base sequence in DNA
-Could alter amino acids DNA encodes—> 3D structure of protein may break down—> could have harmful effects, like cause a genetic disorder
Why do some mutations have no effect on protein structure?
-Due to degenerate nature of DNA; some amino acids are encoded by more than one base triplet code
-If one base is substituted for another base, (e.g. CAA → CAG), the mutated codon may still encode same amino acid (e.g. both encode glutamine)
What is a frameshift?
Where a mutation has a very large impact on protein structure if it impacts all base triplets downstream from mutation
What are the causes of a frameshift?
-When a base/multiple bases is inserted, removed or duplicated into genome
-Alters number of bases in DNA sequence; means all triplet codes downstream from mutation will experience a shift
What are the effects of a frameshift?
-Causes all amino acids following mutation to be affected
-If only 1 amino acid in protein is changed in mutation= protein may be able to function as normal
-Frameshift impacts many amino acids so—> much less likely that protein will function as normal
-Eg= Crohn’s Disease
How does DNA replication cause mutations?
-When DNA is replicated—> bases in DNA sequence= read & copied
-Can be errors in replication process—> errors cause mutations
-These are spontaneous
How do mutagenic agents cause mutations?
-Can increase rate at which mutations occur
-Eg; ionising radiation & UV radiation
