Mutations, Transformations, and Plasmids Flashcards
what is a mutation / what classification are most mutations
change in genetic code inherited vertically through division / detrimental or neutral
what is a silent mutation
nothing happens to the amino acid - the genotype changes but the same amino acid is coded for
what is a missense mutation
a change in the encoded amino acid
what is a nonsense mutation
the creation of a premature stop codon - as well as a truncated protein produced
what is a frame shift (Indels)
Insertions or deletions that are not multiples of 3 that change the reading frame of the DNA
is predicting or measuring phenotypic changes from genotypic changes difficult
yes it is often difficult - the organism must be in the right environment for us to see the effects
how many rounds of replication does it take a spontaneous mutation to fix / why
takes two round / because a spontaneous mutation will only change one nucleic acid so only one daughter cell gets it - when that mutated daughter cell replicates again then the mutation will become fixed
how do cells know which amino acid to correct with a spontaneous mutation
cells methylate their DNA so if there is a mutation then the nucleic acid with the least methylation is the mutation and will get repaired
why is water a source of spontaneous mutation / why is oxygen a source of spontaneous mutation
deamination of a cytosine to a uracil / the intermediates of breaking oxygen down are very reactive and can modify residues which can interfere with polymerases to stop replication or transcription
what are transposable elements / what are they called / what do they lead to
they are “jumping genes” that can cut themselves out and reinsert in a different location / called a transposon / lead to large DNA insertions
what binds to the inverted repeats of the insertion sequence and makes a staggered cut in the target DNA / what usually happens to a gene that receives an insertion
transposase / often get disrupted
how does a lab use transposons in bacteria to identify which genes are esential for infection
a transposon is introduced into bacteria - every gene that is non essential becomes mutated because of the transposon - lets you find which genes are used to cause infection
what are induced mutations
occur as a result of environmental mutagens (things like UV light, ionizing radiation, reactive oxygen species)
what is deinococcus radiodurans / what can we learn from it
one of the most radioresistant organisms known / the mechanisms it uses to repair its DNA (homologous recombination)
what is homologous recombination / why is it important
introduction of DNA with two regions of homology into an organism - resulting in a double cross-over / important for genetic evolution
what is the process for the repair of a double stranded break
- nuclease digests 5’ ends of broken strands 2. RecA binds 3’ ssDNA overhangs - mediating strand invasions by complementary base pairing 3. repair polymerase synthesizes DNA 4. invading strand is released - reanealment of the complementary strand of broken DNA occurs 5. DNA synthesis fills in remaining strands 6. DNA ligase restores chromosome
what is horizontal gene transfer / what are the three forms of horizontal gene transfer
the transfer of DNA between organisms / transduction, transformation, and conjugation
what is transduction / what is transformation / what is conjugation
phage transfers DNA from one bacteria to another (phage mediated transfer) / uptake of naked DNA / transfer of DNA by the F-pilus
what are some bacteria that can perform transformation / what is an example of a transformation
Streptococcus pyogenes (strep throat), Streptococcus pneumoniae (pneumonia), Yersinia pestis (plague), Bacillus anthracis (anthrax), and Neisseria meningitidis (meningitis) / putting living non-encapsulated cells into a mouse with dead encapsulated cells and getting a dead mouse
what does transformation require, why? / what pulls the single stranded DNA through the pilus / what recruits the ssDNA to homologous sites for integration
requires pillus because it binds to floating ssDNA and pulls it in / ComEA / RecA
what are plasmids / what must they have / what do they carry
extrachromosomal heritable DNA / must have an origin or replication and terminator / no essential genes but important genes responsible for survival in specific environments (toxins, antibiotic resistance genes, etc) - some encode for transfer between bacteria
what is conjugation / what two origins of replication does a pladmis encode / what cells can conjugation occur in
plasmid mediated vertical transmission by the fertility factor (F-factor) / oriV (vertical inheritance of plasmid) and oriT (trasmission between bacteria) / any species even between species or different domains
what does the plasmid encode for to do conjugation / what does it do
a type IV secretion system pilus / transfers DNA between donor (F+) and recipient (F-) - long rod that mediates attachment
what happens if the F-factor has homology to a region of the F+ cell
homologous recombination between the F- and F+ cell could occur as however the F- would not become F+ because it would not get the entire plasmid
