Unit 2: Week 1 Round-Up

Question 1

what are the two general types of mutations?

Answer 1

spontaneous
induced

Question 2

list examples of spontaneous mutations (4)

Answer 2

base mistakes remove the spoons.

mistakes during replication
base substitution
addition/removal of nucleotides
transposons

Question 3

three types of base substitution?

Answer 3

silent/missense/nonsense

Question 4

addition/removal of nucleotides is called what?

Answer 4

frameshift

Question 5

what is a silent mutation?

Answer 5

no codon change

Question 6

what is a missense mutation?

Answer 6

change AA acid

Question 7

what is a nonsense mutation?

Answer 7

introduce stop codon

Question 8

four types of induced mutations?

Answer 8

chemical mutagens
base analogs
intercalating agents
UV/X rays

Question 9

what are base analogs? what do they do?

Answer 9

chemicals that look like bases. stop the chain.

Question 10

what do UV/Xrays do?

Answer 10

break/form bonds

Question 11

what are intercalating agents?

Answer 11

insert/bind itself into the DNA

Question 12

name the three virus shapes?

Answer 12

icosahedra
helical
complex

Question 13

what is transduction? how does it work?

Answer 13

mechanism of HGT. DNA is transferred via a bacteriophage.

Question 14

what generates a transducing particle? i.e. what’s the big deal about transduction?

Answer 14

error in phage replication cycle

Question 15

generalized transduction:
- Bacterial chromosomal DNA horizontally transferred via…
- What type of DNA is packaged in virion
- Error occurs during…
- Result of transduction

Answer 15

-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

Question 16

specialized transduction:
- Bacterial chromosomal DNA horizontally transferred via…
- What type of DNA is packaged in virion
- Error occurs during…
- Result of transduction

Answer 16

• 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

Question 17

what two types of transduction did we study in class?

Answer 17

generalized and specialized

Question 18

where does the error in generalized transduction occur?

Answer 18

packaging

Question 19

where does the error in specialized transduction occur?

Answer 19

excision

Question 20

is specialized transduction lysogenic or lytic?

Answer 20

lysogenic only

Question 21

is generalized transduction lysogenic or lytic?

Answer 21

either

Question 22

what proportion of specialized transducing cells contain effective phage DNA?

Answer 22

0

Question 23

what proportion of generalized transducing cells contain effective phage DNA?

Answer 23

1 transducing particle (1 wrong)
Rest are lytic/lysogenic (contain phage DNA)

Question 24

list bacterial defenses against foreign DNA (3)

Answer 24

1. preventing phage attachment (by capsules)
2. restriction-modification systems
3. CRISPR

Question 25

how do bacteria prevent phage attachment?

Answer 25

capsules

Question 26

what are restriction modification systems?

Answer 26

allows bacteria to distinguish/degrade non-self DNA

Question 27

what are the two outcomes of restriction modification systems?

Answer 27

bacteria wins (no phage)
phage wins

Question 28

describe the conditions for the bacteria to win restriction modification system

Answer 28

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

Question 29

describe the conditions for phages winning the restriction modification system

Answer 29

RESTRICTION ENZYME DOES NOT DEGRADE METHYLATED DNA.
1.
2.
3.
4.

Question 30

is methylated DNA degraded by restriction enzyme?

Answer 30

no

Question 31

is unmethylated DNA degraded by restriction enzyme?

Answer 31

yes

Question 32

methylation status vs. degradation status

Answer 32

methylated = not degraded
unmethylated = degraded

Question 33

what is the most important aspect of CRISPR as a bacterial defense against foreign DNA?

Answer 33

keep snapshot of DNA of former infections to develop “memory” to past infections and will chew them up