Bacterial Genetics & Molecular Biology

Question 1

How does bacteria become drug resistant?

Answer 1

mutation and genetic exchange

Question 2

What are 3 major molecular targets for antimicrobials?

Answer 2

bacterial replication, gene expression, and cell wall

Question 3

What did James Watson and Frances Crick do?

Answer 3

worked on the structure of DNA with a double helix

Question 4

T/F: Watson and Crick were the only ones who were working on the structure of DNA

Answer 4

False! Wilkins, Stokes, Wilson, Franklin, and Gosling also worked on it

Question 5

Who came up with the central dogma of DNA?

Answer 5

Crick

Question 6

What is the idea of the central dogma?

Answer 6

DNA–> RNA via transcription
RNA–> protein via translation

Question 7

What is replication?

Answer 7

DNA synthesis by DNA dependent DNA polymerase

Question 8

What is transcription?

Answer 8

mRNA synthesis by RNA polymerases on a DNA template

Question 9

What is translation?

Answer 9

protein synthesis by ribosomes with tRNA and associated factors

Question 10

How do complexity of DNA correlate with transposons?

Answer 10

more complex= more transposons
so humans have more

Question 11

What is bacterial DNA present on?

Answer 11

circular chromosome, transposons, and plasmids

Question 12

How does bacteria replicate?

Answer 12

starts as single circular chromosome and then 2 replication forks going in opposite directions, separating via binary fission to end up with 2 circular daughter DNA molecules

Question 13

T/F: DNA can only polymerize in 5–> 3 direction on the template

Answer 13

True
There is a forward (leading strand) and backward direction (lagging strand) in a 5—-> 3 direction via DNA polymerase

Question 14

T/F: bacteria can have only one plasmid

Answer 14

False!
They can have one or more

Question 15

What can plasmids carry?

Answer 15

protein coding regions with colonization factors, virulence determinants, antibiotic resistance, conjugation pill, and metabolic pathways

Question 16

What is an R plasmid?

Answer 16

resistance plasmid

Question 17

What is Campbell Recombination?

Answer 17

plasmids sharing a region (>400bp) readily join together by cross-over homologous recombination

Question 18

What is a recombinase?

Answer 18

an enzyme that recognizes motifs and can move to plasmid or back and possibly even inactivating an existing gene
- in temperate phages to cause specialized transduction

Question 19

What encodes the recombinase enzyme?

Answer 19

Transposons

Question 20

How do transposons allow for movement between cells?

Answer 20

Some transposons contain genes coding for bacterial surface pilli allowing them to move between cells called conjugative transposon
- integrate into chromosome or plasmid

Question 21

What is a gene?

Answer 21

changes in DNA that lead to heritable phenotypes

Question 22

What’s a promoter?

Answer 22

sequence in DNA that binds RNA polymerase

Question 23

T/F: eukaryotic RNA can encode more than 1 protein

Answer 23

False!
Only prokaryotic RNA

Question 24

What are important targets for specific antibiotics?

Answer 24

bacterial and eukaroytic ribosomes

Question 25

What are the 3 ways bacteria can exchange DNA?

Answer 25

transformation, transduction, conjugation

Question 26

What is transformation?

Answer 26

cells take up naked DNA by lysis
- no cell-cell contact required
(only ~1% species but some pathogens)

Question 27

What is transduction?

Answer 27

phages carry host DNA
(most bacteria)

Question 28

What is conjugation?

Answer 28

cells mate through specialized appendages (pili/fimbriae)
- usually between same species

ex: F plasmids
- F+ has plasmid already, F- doesn’t have the plasmid
- can integrate similarly to a phage

Question 29

What is a bacteriophage?

Answer 29

virus that attacks bacteria and replicates it by invading a living cell using the cell’s molecular machinery

Question 30

What are the 2 types of phages?

Answer 30

1. virulent/lytic phages (RNA and DNA)
   - infection of susceptible bacteria leads to destruction of bacteria and release of the new infectious phage
2. temperate/lysogenic phages (DNA) integrates inside
   - depend on growth conditions and phages can either lyse host or integrate into chromosome. can go lytic if conditions change

Question 31

What is Cornyebacterium Diphtheria?

Answer 31

• encoded by a lysogenic phage
• irregular/club shaped gram + rods
• cause diphtheria (stuff in throat) and 20% fatal in children
• vaccine: DTAP

Question 32

What are the 4 ways bacteria have drug resistance?

Answer 32

1. enzymatic medication or degradation of antibiotic (ex: B-lactamase—> why clavulanic acid is added with B-lactams called augmentin)
2. alter the target of antibiotic
3. change flux of antibiotic
4. intrinsic resistance

Question 33

T/F: Replication, transcription, and translation are important targets for antibiotics.

Answer 33

True!

Question 34

When will bacteria will have genetic capacity such as active flagella, pili, or enzymes for capsules?

Answer 34

depends on what environment they are in!

Question 35

What are transposons?

Answer 35

viral-like pieces of DNA that encode an enzyme to allow them excise and integrate elsewhere in the chromosome
- mobile genetic elements
- always encode recombinases
- more transposons, more complex

Question 36

What do plasmids do for bacteria?

Answer 36

give the bacteria extra capacity to make stuff… worrisome because can allow for production of toxins

Question 37

What does RNA polymerase recognize?

Answer 37

a degenerate motif in the DNA

Question 38

How does erythromycin work?

Answer 38

inhibits protein synthesis by binding to ribosome and stopping translation

Question 39

Which bacteria is shown to have more drug resistance and is an area of interest currently?

Answer 39

gram -
(remember gram + have the thick peptidoglycan wall so this is a big target for many antibiotics)