Lecture 12: Bacterial Genetics Flashcards
what are mutations?
change of nucleotide sequence from a DNA level
how do bacteria acquire genetic diversity?
evolution & adaptations
horizontal communication
gene exchange
vertical communication
new mutation is formed
what is a mutant?
different genotype that carries the change
are mutations heritable?
yes
parental is the ( )
wild type
replication error rate
10^-6 to 10^-7
what 2 things increases mutation rate?
stresses & mutagens
what are mutagens?
chemicals that induce mutation at higher rates than spontaneous rate
what is the Ames test used for?
tests the ability of a chemical to induce revertant in an auxotroph
auxotroph
bacteria that cannot synthesize histidine
higher the number of colonies the ( ) the potenial
higher
what are the 3 results of mutations?
- neutral
- beneficial
- detrimental
neutral result
no observable change
beneficial result
gain function
detrimental result
lost function
what 2 results can occur from non-selectable mutation?
neutral & detrimental
how can non-selectable mutations be found?
screening
how do we screen for non-selectable mutation?
copy & pasting onto a plate using velvet to compare mutants
point mutation
change in single base pair & mRNA
silent mutation
substitution of 3rd base codon (neutral)
missense mutation
substitution of 1st & 2nd base codon (change in amino acid sequence)
nonsense mutation
amino acid change to a stop codon (detrimental)
frameshift mutation
shifts 1 or 2 basepairs
reversion
a second mutation can reverse the effect of a mutation
revertant
wildtype phenotype
true revertant
wildtype genotype
transformation
uses free DNA as food
conjugation
genetic transfer requiring cell to cell contact
donor vs recipient
donor: plasmid +
recipient: plasmid -
transduction
phages pick up host DNA & transfer into new host
generalized transduction
random packaging of host DNA that creates a defective phage
lytic phage
packages DNA randomly & does not induce a lytic cycle
specialized transduction
not random packaging
what type of phage does generalized transduction use?
defective
what type of phage does specialized transduction use?
temperate
phage conversion?
alteration of phenotype by prophages
no prophage =?
no disease
prophage +
pathogenic
prophage -
harmless
what are 2 examples of defense system that prokaryotes use?
programmed cell death & CRISPR
what does CRISPR stand for?
cluster regularly interspaced short palindrome sequences
adaptive immunity
resistance based on previous infections
cas protein
degrades foreign DNA
restriction enzymes
uses endonucleases
phage exclusion
modified DNA to prevent replication
