Card Set Information
Study guide 3-7
Spontaneous mutations:DNA replication (base tautomerization and isertions or deletions)
Tautomerization-bases are changed by gaining additional hydrogens, they change to a different base.
Insertions-slippage on the synthesized strand
Deletion-slippage on the template strand.
Spontaneous mutations: Depurination and Depyrimidization
Depurination- apurinic sites are formed
Depyrimidization- apyrimidic sites are formed
This happens through cleavage of the base
Induced Mutations:Base Analogs
A chemical mutagen- changes the base to another type of base that doesn't pair normally
Induced Mutations:DNA-modifying agents
Chemical mutagen-alters bases in the DNA causing them to mispair
Induced Mutations:Itercalating agents
Chemical mutagen- distorts DNA to induce single nucleotide insertions and deletions.
Induced Mutations:UV light
Physical mutagen-results in thymine dimers.
Characterize the following mutations: Forward
Forward-wild type > mutant
Reverse- mutant > wild type
Suppressor- reversion involving second mutation at a different site than O.G. mutation.
Describe the following types of point mutations, along with what they change:
Silent- Codon for A.A. > Different codon for same A.A.
: Codon for A.A. > Codon for different A.A.
Nonsense- Sense codon > Stop codon
Frameshift- Insertion or deletion of 1 or more BPs
Explain what a conditional mutation is:
A mutation expressed only under certain environmental conditions.
Distinguish between a prototrph and auxotrophic mutant
Auxotrophic mutant-One that is unable to make an essential molecule.
Arises from a mutation in a prototroph
Has a conditional phenotype
Describe the effects of the following non-coding sequence mutations: Operator, promoter, tRNA and rRNA
Operator-Repressor doesn't bind
Promoter- RNA poly doesn't bind
tRNA and rRNA-disrupts translation
Describe how the following methods detect or select for mutations: Replica Plating
Used for screening and detection of auxotrophs. Get a replica block and grow it on a bunch of different mediums.
Describe how the following methods detect or select for mutations: Ames Test
Grow bacteria with mutagen, w/out mutagen, and w/ mutagen in liver extract. See what happens!
Uses His residue
Uses Auxotrophic Salmonella
Discuss the following DNA repair mechanisms: Excision repair: Nucleotide and base
Nucleotide-UvrABC repair enzyme comes in and removes damaged nucleotides. It is filled by DNA poly I and sealed w/ Ligase
Base-Uses DNA glyosylases ro remove unnatural bases. AP endonucleases recognize damaged DNA and nick the backbone at damage. DNA poly removes, and then fills in gap. Ligase seals.
Discuss the following DNA repair mechanisms: Direct repair photoreactivation and removal of alkyl groups
Photoreactivation-uses light to split apart thymine dimers.
Alkyl groups- removed by
Alkyltransferase or Methylgaunine Methyltransferase
Discuss the following DNA repair mechanisms: Mismatch repair
Mismatch correction enzyme scans new strands of DNA, removes them and replaced by DNA poly I and sealed by ligase. Old DNA is methylated, new isn't.
Discuss the following DNA repair mechanisms:Recombinational repair
Repairs both DNA strands.
Involves recombination with an undamaged molecule
RecA catalyzes recombination.
Grabs DNA from sister DNA.
Discuss the following DNA repair mechanisms:SOS response
Used to repair excessive damage that halts replication
RecA protein initiates recombination repair
RecA acts as protease, destroying repressor protein (increasing production of excision repair enzymes)
Life or death situation
Distinguish between vertical gene transfer vs horizontal gene transfer
Vertical- Parents to progeny, in eukary this introduces genetic variation. Prokary do no do this.
Horizontal- genes from independent mature organisms are transferred to one another. Creates a stable recombinant having both donor and recipient.
During HGT, it is the Donor DNA
During HGT it is the DNA in the recipient
During HGT it is a partially diploid cell. Caused by exogenote genes being the same as those present in the recipient.
Identify the 4 outcomes of HGT
Population of stable recombinant
1-Integration of exogenote
2-Exogenote self replicates (plasmid)
No stable recombinant
3-Exogenote cannot self replicate
4-Host restriction (host cuts it up)
Briefly characterize the following recombination mechanism: Homologous recombination
A reciprocal change between a pair of DNA molecules with same nucleotide sequence.
Briefly characterize the following recombination mechanism:site specific recombination
Viral genomes integrated into hosts