Microbial Genetics

Question 1

What are the two types of bacterial genetic material?

Answer 1

1) bacterial chromosome

2) plasmid

Question 2

What’s the difference between bacterial chromosome and plasmid?

Answer 2

1) chromosome is a single, large circular DNA molecule. it contains all genes for survival
2) plasmid is a small, circular DNA moledule. copy number varies

Question 3

Sometimes plasmid may integrate into bacterial chromosome, what is this called?

Answer 3

episomes

Question 4

Human genomes contain 23 chromosomes, what about bacterial genomes?

Answer 4

one

Question 5

Human cells are diploid, what about bacteria?

Answer 5

haploid (only 1 copy)

Question 6

Are exons and introns present in bacteria?

Answer 6

no

Question 7

Are histones present in bacteria?

Answer 7

no

Question 8

How do transcription and translation differ between humans and bacteria?

Answer 8

In bacteria, transcription and translation are coupled because they lack nucleus.
In humans, transcription and translation are two separate processes

Question 9

Genes on bacterial chromosome are polycistronic, what does that mean?

Answer 9

one promoter can drive transcription of multiple genes whereas human genes are monocistronic

Question 10

Repression is ____ type of gene regulation while activation is ____ type of gene regulation

Answer 10

repression –> negative

activation –> positive

Question 11

Describe repression

Answer 11

a repressor is required to stop gene transcription, meaning gene transcription is always on otherwise

Question 12

Describe activation

Answer 12

an activator is required to start transcription because RNA polymerase alone does not have enough affinity for promoter region

Question 13

What are the two types of gene transfer in bacteria?

Answer 13

1) vertical

2) horizontal

Question 14

Which type of gene transfer is this, genes are passed via replication to progeny?

Answer 14

vertical

Question 15

What are the three types of horizontal gene transfer?

Answer 15

1) transformation
2) conjugation
3) transduction

Question 16

True or False. No new DNA is acquired during cell division

Answer 16

True

Question 17

Bacterial multiplication is a sexual or asexual process?

Answer 17

asexual

Question 18

Is evolution of new traits like resistance to antibiotics a slow or fast process in bacteria?

Answer 18

SLOWWWW

Question 19

How do bacteria become antibiotic resistance and produce new virulence factors so fast?

Answer 19

horizontal gene transfer

Question 20

True or False. Horizontal gene transfer can occur only between same species of bacteria

Answer 20

False. it can occur between species within genus as well

Question 21

What is homologous recombination?

Answer 21

exchange of DNA between two DNA molecules based in homology

Question 22

Describe the process of homologous recombination

Answer 22

1) exchange of DNA between 2 pieces of DNA with homologous sequence
2) recombination is aided by a recomination protein such as RecA
3) linear DNA is degraded
Note that DNA that was incoporated is now passed down to daughter cells and becomes a permanent part of the genome

Question 23

Which type of horizontal gene transfer is this involves uptake of free DNA from the environment?

Answer 23

transformation

Question 24

Which type of horizontal gene transfer involves DNA transfer directly from one bacterial cell to another through cell contact?

Answer 24

conjugation

Question 25

Which type of horizontal gene transfer involves the transfer of bacterial DNA via bacteriophage?

Answer 25

transduction

Question 26

Which type of horizontal gene transfer allow bacteria to gain new traits quickly?

Answer 26

transformation

Question 27

Which type of horizontal gene transfer allow one bacterium to acquire new DNA from another viable bacterium?

Answer 27

conjugation

Question 28

Briefly describe the process of transformation

Answer 28

1) a bacterium (donor cell) lyses and releases DNA fragments to environment 2) DNA enters recipient cell and is integrated into its DNA via homologous recombination

Question 29

True or False. DNA transfer in conjugation is bi-directional

Answer 29

False. it is uni-directional

Question 30

What is F factor?

Answer 30

Fertility factor that carrier genes, tra operon, that encode components for sex pillus

Question 31

Briefly describe the transfer of DNA from F+ to F-

Answer 31

F+ extends out a sex pilus to recipient (F-). A single strand of plasmid is transferred.

Question 32

Briefly describe the transfer of DNA between Hfr and F-

Answer 32

HFR has the F factor integrated into its chromosome, Part of the genome will get transferred but before it finishes the unstable sex pilus will disappear. Homologous recombination will occur and the F- received new bacterial genes

Question 33

In conjugation between F+ and F-, are bacterial genes transferred?

Answer 33

No, only a single strand is transferred (F factor)

Question 34

The transfer of bacterial DNA via a bacteriophage

Answer 34

transduction

Question 35

What are the two different life cycles of a bacteriophage?

Answer 35

1) lytic/ virulent phage | 2) temperate phage

Question 36

What occurs in lytic phage?

Answer 36

lytic replication upon entry

Question 37

What occurs in temperate phage?

Answer 37

lysogeny (integration into the chromosome) can excise and undertake lytic replication

Question 38

Where does a lytic phage incorporate bacterial chromosomal DNA into?

Answer 38

its phage head

Question 39

When the phage infects another bacteria, the DNA can be incorporated into its chromosome via which process?

Answer 39

homologous recombination

Question 40

Lysogenic phage incorporates into the chromosome as a what?

Answer 40

prophage

Question 41

What leads to conversion of lysogenic phage into lytic lifecycle

Answer 41

an event such as UV damage (basically virus sense trouble to host)

Question 42

What occurs after excision from the genome?

Answer 42

a small portion of the chromosome, directly adjacent to where the phage was integrated is packaged into a phage head

Question 43

Which of the three horizontal gene transfers utilizes free DNA?

Answer 43

transformation

Question 44

Which of the three horizontal gene transfers require cell-to-cell contact?

Answer 44

conjugation

Question 45

Which of the three horizontal gene transfers require homologous recombination?

Answer 45

transformation transduction conjugation ( only in Hfr with F-)

Question 46

What are the three general categories of antibiotic resistance?

Answer 46

1) intrinsic 2) chromosome-mediated 3) plasmid-mediated

Question 47

Which of the three types of antibiotic resistance is not transferable (horizontally) between bacteria?

Answer 47

intrinsic

Question 48

Which of the three types of antibiotic resistance is not increasing among bacterial populations?

Answer 48

intrinsic

Question 49

What's an example of intrinsic antibiotic resistance?

Answer 49

lack of cell wall (mycoplasma)

Question 50

Which of the three types of antibiotic resistance allow chromosomal genes encoding antibiotic resistance?

Answer 50

chromosome-mediated

Question 51

How does chromosomal-mediated antibiotic resistance arise?

Answer 51

1) random mutation during replication | 2) acquisition of DNA through horizontal gene transfer and incorportation into the genome via homologous recombination

Question 52

What are examples of chromosomal-mediated antibiotic resistance?

Answer 52

1) ribosomal proteins 2) penicillin-binding proteins 3) DNA gyrase

Question 53

Where are plasmid-mediated antibiotic resistance genome located?

Answer 53

plasmid

Question 54

Commonly plasmids carry genes that encode proteins for what?

Answer 54

1) degradation of antibiotic 2) modification of antibiotic 3) efflux pump to pump antibiotic out of cell

Question 55

What is R-factor?

Answer 55

resistance factor, a conjugative plasmid

Question 56

What are the two components to R-factor?

Answer 56

1) resistance transfer factor | 2) resistance determinant

Question 57

What is resistance transfer factor?

Answer 57

similar to F factor that it encodes all proteins needed for conjugation

Question 58

What is resistance determinant?

Answer 58

gene(s) for drug resistance

Question 59

What are transposons?

Answer 59

mobile DNA elements that can transfer themselves (or a copy) from one molecule to another

Question 60

What does a simple transposon contain?

Answer 60

1) indirect repeat sequences on each end 2) single gene for transposae, TnpA, enzyme required for "jumping" 3) contain a single or multiple antibiotic resistance gene(s)

Question 61

What are some ways transposons can pass down multi-drug resistance?

Answer 61

1) between two chromosomes 2) between two plasmids 3) between on of each

Question 62

What are integrons?

Answer 62

diverse group of genetic elements that encode a site-specific recombination system that can capture gene cassettes and express them in a coordinated manner under the control of the integron promoter

Question 63

What are pathogenicity islands?

Answer 63

region of bacterial chromosome acquired through horizontal gene transfer, often carry coordinately regulated virulence genes surrounded by insertion sequences (like a large tranposon)