EXAM 1 Bacterial Genetics

Question 1

___ and ___ are coupled in bacteria. what is the result?

Answer 1

• transcription and translation
• the result is the ability to quickly replicate

Question 2

DtxR regulates ___ genes within ___ operons

Answer 2

• 53
• 26

Question 3

___ recognize specific promoter sequences and direct the RNA polymerase complex where to bind within the DNA

Answer 3

sigma factors

Question 4

bacteria contain numerous sigma factors that mediate responses to diverse ___

Answer 4

stresses

Question 5

how do bacteria change their genetic makeup (how do they evolve)?

Answer 5

• since they are haploid organisms that divide by binary fission, they can’t increase genetic diversity via sex
• options for increasing genetic diversity are mutation or horizontal gene exchange mechanisms

Question 6

what are 4 main mechanisms of genetic change and diversification in bacteria?

Answer 6

• point mutation
  
  • nucleotide change
  • nucleotide insertion
  • nucleotide deletion
• gene duplication
• gene deletion
• chromosomal rearrangement
  
  • inversion
  • intragenic recombination

Question 7

during stressful conditions, some bacteria become ___, acquiring mutations at an increased rate

Answer 7

hypermutable

this assures that there are ample variants ready to adapt to new circumstances

Question 8

describe point mutations

Answer 8

• can impact expression of virulence factors and the sensitivity of antibiotic targets
• antibiotic targets usually come with a fitness cost

Question 9

gene duplication and amplification constitues an important adaptive mechanism in bacteria. describe.

Answer 9

• resistance to antibiotics like sulphonamide, trimethoprim, and beta-lactams can be conferred by increased gene dosage through duplication/amplification of antibiotic hydrolytic enzymes, target enzymes, or efflux pumps

Question 10

describe horizontal gene transfer

Answer 10

genes are transferred within a bacterial population

• bacterial transformation - one bacteria releases a piece of its DNA which another bacterium will pick up
• bacterial transduction - bacterial phage infects one bacteria and can package the bacterial DNA; the phage can then go on and infect other bacteria
• bacterial conjugation - some bacteria can use form conjugation bridges to allow the transfer of DNA molecules from the donor bacteria to the recipient

Question 11

what is transformation?

Answer 11

DNA is taken up directly by cells

Question 12

bacteria able to take up DNA are said to be ___

Answer 12

competent

Question 13

some bacteria take up DNA all of the time. they are said to be ___, and express DNA uptake systems.

Answer 13

naturally competent

Question 14

some bacteria take up DNA mostly from the same genus, requiring what?

Answer 14

specific sequences on the incoming DNA

Question 15

most naturally competent bacteria take up ___ DNA

Answer 15

linear

Question 16

describe griffith’s classic 1928 experiment demonstrating natural transformation in strep. pneumoniae

Answer 16

Question 17

___ is the transfer of DNA mediated by bacteriophages

Answer 17

transduction

Question 18

transduction is found wherever you find ___

Answer 18

bacteria

Question 19

in transduction, virus ___ within bacteria

Answer 19

replicate

Question 20

phages can go through ___ or ___ phases

Answer 20

lytic or lysogenic

Question 21

___ can carry imporant fitness and virulence determinants

Answer 21

prophage

Question 22

___ occurs when bacterial genes are packaged by phage and subsequently transferred to other bacteria

Answer 22

transduction

Question 23

what does conjugation describe?

Answer 23

bacterial sex

Question 24

what are the 4 plasmid types?

Answer 24

• fertility f-plasmids
• col plasmids
• virulence plasmids
• resistance (R) plasmids

Question 25

what type of plasmids contain tra genes for transfer, are capable of conjugation, and result in the expression of sex peli?

Answer 25

fertility f-plasmids

Question 26

what type of plasmids contain genes that code for bacteriocins (proteins that can kill other bacteria)?

Answer 26

col plasmids

*some are also toxic to host cells (genotoxins)

Question 27

what type of plasmids encode virulence factors and can convert a bacterium into a pathogen?

Answer 27

virulence plasmids

Question 28

what type of plasmids contain genes that provide resistance against antibiotics or poisons, and were historically known as R-factors before the nature of plasmids was understood?

Answer 28

resistance (R) plasmids

Question 29

some plasmids can only be transferred by tagging along with other plasmids that contain which genes?

Answer 29

tra genes

Question 30

what are transposable elements?

Answer 30

DNA elements that move from one place in bacterial DNA to another

Question 31

transposable elements can transfer genes to a new location or disrupt genes when they ___

Answer 31

insert

Question 32

transposable elements can carry ___ and ___ resistance genes

Answer 32

virulence and antibiotic

Question 33

what happens in replicative transposition?

Answer 33

the transposable elements leave a copy behind

Question 34

in transposable elements, ___ will move the transposon to a new site

Answer 34

direct transposition

Question 35

what are pathogenicity islands (PAIs)?

Answer 35

many virulence genes in compact, distinct genomic islands

Question 36

pathogenicity islands are acquired by ___

Answer 36

horizontal gene transfer

Question 37

pathogenicity islands have different ___ content than the rest of the bacterial chromosome

Answer 37

G-C%

Question 38

natural populations of many pathogens have a clonal structure. in some cases, single clones are responsible for ___

Answer 38

geographically widespread disease