BMSC 210 part 3

tasnimjaisee's version from 2017-11-05 20:55

Lecture 12

Question Answer
MutationHeritable change in DNA sequence that can lead to a change in phenotype (observable properties of an organism)
MutantA strain of any cell or virus differing from parental strain in genotype
Wild‐type strainStrain isolated from nature
Selectable mutationsgrowth advantage under certain conditions
Nonselectable mutationsadvantage nor a disadvantage over the parent
Detecting such mutations requires examining a large number of colonies and looking for differences (Selectable/NonSelectable)Nonselectable
Replica platingIdentifying cells with a nutritional requirement for growth
auxotrophmutant organism requiring particular additional nutrient that the normal strain does not
Induced mutationsMade enviornmentally or deliberarely
Spontaneous mutationsOccur without external intervention
Point mutationsChange only one base pair
Silent mutationDoes not affect amino acid sequence
Missense mutationAmino acid changed; polypeptide altered
Nonsense mutationCodon becomes stop codon; polypeptide is incomplete
What kind of results would occur from a Missense mutation?Faulty protein
What kind of results would occur from a Nonsense mutation?Incomplete protein
What kind of results would occur from a Silent mutation?Normal protein
What kind of results would occur from a Wild type?Normal protein
Frameshift mutationsDeletions or insertions; complete loss of gene function
___ mutations are typically reversiblePoint
ReversionAlteration in DNA that reverses the effects of a prior mutation
RevertantStrain in which original phenotype is restored
Revertant TypesSame‐site revertant - Second-site revertant
Same‐site revertantmutation is at the same site as original mutation
Second‐site revertantmutation is at a different site in the DNA
For most microorganisms, errors in DNA replication occur at a frequency of?10^-6 ro 10^-7 per kb
DNA viruses have error rates of?100–1000x greater
The mutation rate in RNA genomes is _____‐fold higher than in DNA genomes1000
RNA polymerases have ____ capabilities but, like DNA, ____ mechanisms do not existPROOFREADING - Repair
Ames testpractical use of bacterial mutations to detect for hazardous chemicals
Ames test: Looks for an ____ in mutation of bacteria in the presence of suspected ____Increase - Mutagen
Classes of chemical mutagensNucleotide base analogs - Chemical modifiers - Frameshift mutators
chemical mutagens: Nucleotide base analogsresemble nucleotides
Two main categories of mutagenic electromagnetic radiationNon-Ionizing & Ionizing
Mutagenesis: Non-IonizingPurines and pyrimidies absorbing UV - Pyrimidine dimer is one effect of UV radiation
Mutagenesis: IonizingIonize water and produce free radicals - Free radicals damage macromolecules in the cell
Three types of DNA repair systemsDirect reversal - Repair of single-strand damage - Repair of double-strand damage
DNA repair systems: Direct reversalRecognizable Mutated base; Repaired without referring to other strand
DNA repair systems: Repair of single‐strand damagedamaged DNA is removed and repaired using opposite strand as template
DNA repair systems: Repair of double‐strand damageBreak in the DNA • Requires more error‐prone repair mechanisms
SOS regulatory systemReplication to proceed and cell to replicate, but errors are more likely
Translesion synthesisDNA to be synthesized with no template
The SOS “regulon”: UvrA proteinError‐free DNA repair
The SOS “regulon”: UmuCD proteinError‐prone DNA repair
Mutants can be isolated that are ______, or alternatively, have ____ mutation rateshyperaccurate - increaed
Mutator strainsbacteria that have permanently increased mutation rates

Lecture 12

Question Answer
Selective mediumdetect rare genetic recombinants