Section 7: Mutation Flashcards
Wild type organism
strain whose properties are similar to the organism isolated from nature
Spontaneous Mutations (vs. induced)
occur in natural environment
- base substitutions
- removal/addition of nucleotides
- transposons
Base substitutions (spontaneous mutation)
incorrect base substituted in DNA during replication
- one: point mutation
- if leads to different amino acid: missense substitution
- if stop codon created: nonsense substitution
Removal or Addition of Nucleotides (spontaneous mutation)
changes in way DNA sequence is read (changes codon/reading frame) = frameshift mutation
Transposons (spontaneous mutation)
DNA segments moving from one site to the other = jumping genes (hehe)
Induced Mutations (vs. spontaneous)
change in DNA that results in a mutagen such as chemical agents and radiation.
Chemical agents (induced mutation)
alters the binding of DNA molecule
- Alkylating agents (add alkyl groups to nitrogenous bases, altering hydrogen bonding properties)
- base analogs (compounds that resemble bases and thus incorporated into DNA in place of natural bases)
- intercalating agents (planar molecules that wedge in between base pairs in DNA, and do not change bonding patterns)
Radiation (induced mutation)
Uv light (thymine dimers) and X-rays (single and double stranded breaks in DNA)
Repair of mutations
Mismatched/excision repair
OR
SOS repair (last ditch effort to save DNA)
Mutant selection
to study function of genes, mutations are induced (specific mutants) to understand normal gene function
Nutritional Mutants
Prototrophs: cells that grow without added growth factors (natural strains)
Auxotrophs: cells that grow only with added growth factors added in the laboratory
Conditional Lethal Mutants
mutants defective for synthesis of an essential macromolecule under specific conditions (aka grown under wrong conditions you DIE!)
eg. temperature sensitive mutants
