chapter 6 part 1

Question 1

in what ways are bacteria useful genetic models

Answer 1

• genome simplicity (fewer genes/bases)
• haploid genomes
• short generation times (min)
• enormous numbers of progeny
• ease of propagation
• numerous heritable differences

Question 2

what are bacterial genomes usually composed of

Answer 2

single chromosome, which carries mostly essential genes

Question 3

bacterial chromosome structure

Answer 3

covalently closed circular molecule of double-stranded DNA

Question 4

how many base pairs do bacterial genomes usually have

Answer 4

few thousand to few million

Question 5

plasmids

Answer 5

small double-stranded circular DNA molecules containing non-essential genes

Question 6

are plasmids smaller or larger than bacterial chromosomes

Answer 6

smaller

Question 7

plasmids are used in a variety of ____________ _____ ______________

Answer 7

recombinant DNA applications

Question 8

2 types of plasmids

Answer 8

1. R (resistance) plasmid
2. F (fertility) plasmid

Question 9

R plasmid

Answer 9

carries antibiotic resistance genes that can be transferred to recipient cells

Question 10

fertility plasmid

Answer 10

contains genes that promote its own transfer from donors to recipients

Question 11

high-copy number plasmids

Answer 11

plasmids that can replicate independently of the bacterial chromosome so that the number of plasmids per cell can increase rapidly

Question 12

low-copy number plasmids

Answer 12

present in 1/2 copies per bacterial cell and usually cannot replicate independently of the bacterial chromosome

Question 13

3 methods of recombination in prokaryotes

Answer 13

1. conjugation
2. transformation
3. transduction

Question 14

conjugation overview

Answer 14

transfer of replicated DNA from a donor to a recipient

Question 15

transformation overview

Answer 15

uptake of DNA from the environment

Question 16

transduction overview

Answer 16

transfer of DNA from one bacterium to another by a viral vector

Question 17

each method of recombination involves what

Answer 17

one-way transfer of genetic material from a donor bacterial cell to a recipient cell

Question 18

what is the hollow tube called where genetic information is transferred in conjugation

Answer 18

conjugation pilus/tube

Question 19

which recombination method involves the direct physical union of two bacteria

Answer 19

conjugation

Question 20

what is the ability to act as a donor determined by

Answer 20

fertility factor (F factor)

Question 21

does the donor or recipient possess an F factor

Answer 21

donor - F+ cells

Question 22

does the donor or recipient lack an F factor

Answer 22

recipient - F- cells

Question 23

what is conjugation controlled by

Answer 23

genes carried on the F plasmid

Question 24

what does the F factor plasmid control

Answer 24

40 genes that control conjugation

Question 25

what do the F factor genes direct formation of

Answer 25

exported structure that will move the donor DNA into the recipient cell

Question 26

relaxosome

Answer 26

cuts one strand of F factor DNA, triggering DNA replication, and movement of F factor DNA to the recipient cell where its own DNA replication occurs

Question 27

exoconjugant cell

Answer 27

term for the recipient cell after conjugation - recipient cell with its genetic information modified by receiving DNA from the donor cell

Question 28

mechanism of conjugation 1

Answer 28

- conjugation plus forms between donor/recipient cells - gene expression from F factor produces protein complex called relaxosome - relaxosome binds to origin of transfer (ori) on F factor and cleaves one phosphodiester bond on T (transfer) strand of F factor - relaxosome partially degenerates, leaving relaxase attached to free 5'end of T strand

Question 29

mechanism of conjugation II

Answer 29

- relaxase facilitates movement of t strand through conjugation pilus into recipient cell - T strand transfer across pilus is accompanies by a specialized process called rolling circle replication - rolling circle replication uses non-transferred DNA strand as a template and displaces the 5' end of T strand, freeing it for transfer into recipient - recipient cell uses imported DNA as template for replication

Question 30

at the end of conjugation, which cell contains a complete double-stranded F factor

Answer 30

both cells

Question 31

how many insertion sequences does a large F factor contain

Answer 31

4

Question 32

insertion sequence (IS) elements

Answer 32

mobile segments of bacterial NA that can transpose themselves to new locations (like transposons)

Question 33

episome

Answer 33

when circular elements like the F factor or plasmid integrate into the bacterial chromosome

Question 34

Hfr cells (high frequency recombination)

Answer 34

when an F factor forms an episome in bacteria

Question 35

how does gene transfer to recipient cells from Her strains occur

Answer 35

rolling circle replication (F+ x F- conjugation)

Question 36

what is not accomplished in gene transfer from Hfr cell

Answer 36

complete transfer of bacterial chromosome - it is too long

Question 37

what happens when the segment of T strand DNA enters the recipient in transfer from Hfr cell

Answer 37

used to generate a double-stranded linear fragment

Question 38

can linear DNA in the recipient cell re-circularize?

Answer 38

no

Question 39

where does homologous recombination occur?

Answer 39

between transferred linear DNA and circular chromosome of recipient

Question 40

how may the new exconjugant cell acquire 1+ donor genes?

Answer 40

homologous recombination between linear DNA and circular chromosome

Question 41

F' cells

Answer 41

donor cells carrying and F factor derived from excision of F factor from Hfr chromosome

Question 42

F' donor bacterium contains

Answer 42

functional F factor derived from aberrant (imperfect) excision of F factor from an Hfr chromosome)

Question 43

what does resulting F' factor contain

Answer 43

all its own DNA plus a segment of the bacterial chromosome

Question 44

what are exconjugants that contain a complete F' factor called

Answer 44

partial diploids

Question 45

partial diploids

Answer 45

contain 2 copies of bacterial chromosome genes found on the F' factor

Question 46

how is partial diploidy retained

Answer 46

as a characteristic of the exconjugants and their descendants

Question 47

merozygote

Answer 47

a state when a partially diploid bacterial cell is produced