Module 6b Flashcards
Mutations
Heritable changes in a genome
DNA damage and mutations are similar
False
How is DNA damage mediated
Repair to continue cell function
Can DNA damage lead to a mutation
yes, if the repair changes the base sequence
When can changes in the genome occur
within a coding region of genes, a regulatory region of an operon, untranslated RNAs or regions between genes
All mutations result in phenotypic change from the parent cell
false
Spontaneous mutations
Errors in normal DNA replication or DNA repair
1st Common spontaneous mutaion
Base changes
Base changes
The wrong base is inserted into the new strand by DNA polymerase
2nd Common spontaneous mutation
Base additions and deletions
What causes polymerase errors
Bases shifting to alternate isomers
Is an error considered a mutation before the genome is replicated and passed on
No
Mutant
organism with the changed genome that was passed from a parent
Spontaneous mutation #3
Slippage
Slippage
An advancing polymerase loses track of the template or new strand leading to deletion or insertion
Induced mutations
Result from exposure to a condition or chemical that causes more errors in DNA replication
Mutagens
cause elevated rates of mutations
Bases analogues
gets inserted as a base
mutagen
DNA-modifying agents
change base chemistry to allow easier misspairing
mutagen
Physical agent
Damage DNA (radiation)
Mutagen
Intercalating agents
Cause slippage by inserting between two base
Mutagen
Has a much higher frequency of isomer switching affecting the subsequent round of replication by pairing with a different base
Base analogues
Mutagens that change a bases structure that cause specific damage to certain bases
DNA-modifying agents
Methyl-nitrosoguanidine
Adds methyl group to G causing a pair with T not C
Insert themselves between bases in the double helix resulting in helical distortion
Interlacating agents
Interlacating agents in low concentrations
cause slippage and a mutation
Interlacating agents in high concentrations
NOT a mutagen
Stops replication of the DNA and therefore results in death not passage to the next generation
Causes affected bases to not function as a template that must be repaired before replication can occur
Physical agents
Wild type
Organism isolated from its natural environment
Can wild types have different bases in a gene
yes, these are alleles and they are considered a subset of the wild type
Mutants are conventionally cells with changes experienced in the wild
False
They are induced/selected/obtained in the lab
In vitro
in an unnatural setting
Frequency of a mutation depends on
the number of genes that are required for the phenotype
Mutation frequency decreases with the number of genes involved
True
Strategies for isolating mutants
Screening and selecting
Mutant screening
Individual cells are checked to determine if they have the mutant phenotype
This way of finding mutants is typically used when mutants have lost the ability to do something
Screening
Mutant selection
Exposing a population to a condition allowing for growth or survival of the mutant only
This type of mutant isolation allows for testing of a large number of cells
Mutant selection
Auxotroph
unable to grow on media that the wildtype parent can
Revertant strain
Cells that can once again grow on media that their wild type can, but their auxotroph could not
Ames test
Used to determine whether new compounds are mutagenic by measuring the frequency of mutational events
