Unit 2: Week 1 Round-Up Flashcards
what are the two general types of mutations?
spontaneous
induced
list examples of spontaneous mutations (4)
base mistakes remove the spoons.
mistakes during replication
base substitution
addition/removal of nucleotides
transposons
three types of base substitution?
silent/missense/nonsense
addition/removal of nucleotides is called what?
frameshift
what is a silent mutation?
no codon change
what is a missense mutation?
change AA acid
what is a nonsense mutation?
introduce stop codon
four types of induced mutations?
chemical mutagens
base analogs
intercalating agents
UV/X rays
what are base analogs? what do they do?
chemicals that look like bases. stop the chain.
what do UV/Xrays do?
break/form bonds
what are intercalating agents?
insert/bind itself into the DNA
name the three virus shapes?
icosahedra
helical
complex
what is transduction? how does it work?
mechanism of HGT. DNA is transferred via a bacteriophage.
what generates a transducing particle? i.e. what’s the big deal about transduction?
error in phage replication cycle
generalized transduction:
- Bacterial chromosomal DNA horizontally transferred via…
- What type of DNA is packaged in virion
- Error occurs during…
- Result of transduction
-lytic or temperate phages when they induce lytic cycles
- any random piece of bacterial chromosomal DNA
- packaging
- 1 or few transducing particles, the remaining are effective phage particles
specialized transduction:
- Bacterial chromosomal DNA horizontally transferred via…
- What type of DNA is packaged in virion
- Error occurs during…
- Result of transduction
- temperate phage ONLY!
- specific bacterial chromosomal DNA along with some phage DNA (genes next to the integration sites of the prophage)
- excision
- 100% transducing particles and also defective phages
what two types of transduction did we study in class?
generalized and specialized
where does the error in generalized transduction occur?
packaging
where does the error in specialized transduction occur?
excision
is specialized transduction lysogenic or lytic?
lysogenic only
is generalized transduction lysogenic or lytic?
either
what proportion of specialized transducing cells contain effective phage DNA?
0
what proportion of generalized transducing cells contain effective phage DNA?
1 transducing particle (1 wrong)
Rest are lytic/lysogenic (contain phage DNA)
list bacterial defenses against foreign DNA (3)
- preventing phage attachment (by capsules)
- restriction-modification systems
- CRISPR
how do bacteria prevent phage attachment?
capsules
what are restriction modification systems?
allows bacteria to distinguish/degrade non-self DNA
what are the two outcomes of restriction modification systems?
bacteria wins (no phage)
phage wins
describe the conditions for the bacteria to win restriction modification system
RESTRICTION ENZYME DEGRADES UNMETHYLATED DNA.
1. Phage DNA not methylated,
2. Chr. DNA is methylated
3. Phage DNA is degraded, there is no phage replication
4. No phage
describe the conditions for phages winning the restriction modification system
RESTRICTION ENZYME DOES NOT DEGRADE METHYLATED DNA.
1.
2.
3.
4.
is methylated DNA degraded by restriction enzyme?
no
is unmethylated DNA degraded by restriction enzyme?
yes
methylation status vs. degradation status
methylated = not degraded
unmethylated = degraded
what is the most important aspect of CRISPR as a bacterial defense against foreign DNA?
keep snapshot of DNA of former infections to develop “memory” to past infections and will chew them up
