chapter 6 part 1

Question 1

genome simplicity

Answer 1

fewer genes & fewer bases than other organisms

Question 2

haploid genomes

Answer 2

mutations can be observed directly because there i one copy of each gene

Question 3

short term generation times

Answer 3

can be measured in minutes

Question 4

enormous numbers of progeny

Answer 4

allow detection of rare events

Question 5

ease of propagation

Answer 5

bacterial culture is easy & inexpensive & takes up very little space

Question 6

numerous heritable differences

Answer 6

mutations are easily created, identified, isolated, & manipulated for study

Question 7

why are bacteria useful genetic models?

Answer 7

-genome simplicity
-haploid genomes
-short generation times
-enormous numbers of progeny
-ease of propagation
-numerous heritable differences

Question 8

how many chromosomes are bacterial genomes usually composed of?

Answer 8

a single chromosome that carries mostly essential genes

Question 9

is the bacterial chromosome usually circular or linear?

Answer 9

it is a usually circular model of double stranded DNA

Question 10

is a bacterial chromosome big or small compared to eukaryotic genomes?

Answer 10

small
it only contains a few thousand to a few million base pairs

Question 11

how many plasmids do bacteria usually contain?

Answer 11

one or more

Question 12

what are plasmids

Answer 12

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

Question 13

are plasmids usually bigger or smaller than bacterial chromosomes?

Answer 13

smaller

Question 14

how many different kinds of plasmids are found in bacteria?

Answer 14

many different kinds of naturally occurring plasmids are found in bacteria

Question 15

R (resistance) plasmid

Answer 15

• carries antibiotic resistance genes that can be transferred to recipient cells

Question 16

F (fertility) plasmid

Answer 16

• contains genes that promote its own transfer from donors to recipients

Question 17

what are the two types of plasmids

Answer 17

• R (resistance) plasmid & F (fertility) plasmid

Question 18

can plasmids replicate independently of the bacterial chromosome?

Answer 18

yes, so that the number of plasmids per cell can increase rapidly

Question 19

high copy number plasmids

Answer 19

plasmids that replicate independently where there are 50 or more of that plasmid per cell

Question 20

low-copy number plasmids

Answer 20

present in one or two copes per bacterial cell & usually cannot replicate independently of the bacterial chromosome

Question 21

do low-copy number plasmids replicate independently of the bacterial chromosome?

Answer 21

no

Question 22

what are the three ways of recombination in prokaryotes?

Answer 22

conjugation
transformation
transduction

Question 23

conjugation

Answer 23

the transfer of replicated DNA from a donor to a recepient

Question 24

transformation

Answer 24

the uptake of DNA from the environment

Question 25

transduction

Answer 25

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

Question 26

what does each method of recombination involve?

Answer 26

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

Question 27

which form of recombination involves physical contact transfer?

Answer 27

conjugation

Question 28

conjugation in detail

Answer 28

-the donor cell transfers some of its genetic info to a recipient cell

Question 29

in conjugation, what is the genetic info transferred through?

Answer 29

a conjugation pilus or conjugation tube

Question 30

what takes place between the donors & recipients

Answer 30

plasmid that facilitates a one-way-transfer

Question 31

what determines the ability ot act is a donor?

Answer 31

the 'fertility factor' or (F) factor

Question 32

do donor cells have the F factor?

Answer 32

they have the F factor so they are F+, while the recipient cells are called F- and lack an F factor

Question 33

what is conjugation controlled by?

Answer 33

genes carried on the F plasmid

Question 34

how many genes does the F factor (plasmid) encode for?

Answer 34

40 genes that control conjugation

Question 35

what do the F factor genes direct formation of and what does it do?

Answer 35

an exporter structure that will move the donor DNA into the recipient cell

Question 36

what does the relaxosome do?

Answer 36

cuts one strand of F factor DNA, which triggers DNA replication, and movement of F factor DNA to the recipient cel where its own DNA replication occurs

Question 37

what is the recipient cell called after conjugation?

Answer 37

the exoconjugant cell it is the recipient cell with its genetic info modified by receiving DNA from the donor cell

Question 38

mechanism of conjugation 1

Answer 38

1. a conjugation pilus forms between donor & recipient cells 2. gene expression from the F factor produces a protein complex called the relaxosome 3. relaxosome binds the origin of transfer (OriT) on the F factor & cleaves one phosphodiester bond on the T (transfer) strand of the F factor 4. relaxosome partially degenerates, leaving relaxase attached to the free 5' end of the T strand

Question 39

mechanism of conjugation 2

Answer 39

-t strand transfer across the pilus is accompanied by a process called rolling circle replication, which starts at OriT -rolling circle replication uses non-transferred DNA strand as a template & displaces the 5' end of the T strand, freeing it for transfer into the recipient -the recipient cell uses the imported DNA as a template for replication, by the end of the process, both cells contain complete double-stranded F factor

Question 40

how many insertion sequence (IS) elements are there?

Answer 40

4

Question 41

A large component of the F factor consists of four _______ ________ elements

Answer 41

insertion sequence

Question 42

what are IS elements

Answer 42

moble segments of bacterial DNA that can transpose themsleves to new locations (like transposons)

Question 43

when does an episome occur?

Answer 43

when a plasmid integrates into the bacterial chromosome

Question 44

what forms an episome?

Answer 44

when circular elements like the F factor can integrate into the bacterial chromosome

Question 45

what do we call it when the plasmid e=integrates into the bacterial chromosome?

Answer 45

Hfr cells

Question 46

what does Hfr stand for

Answer 46

high frequency recombination

Question 47

is complete transfer of the bacterial chromosome in Hfr accomplished?

Answer 47

no

Question 48

what does gene transfer to recipient cells from Hfr strains occur by?

Answer 48

rolling circle replication

Question 49

can linear dna in the recipient cell re-circularize in Hfr gene transfer?

Answer 49

no

Question 50

where does homologous recombination occur?

Answer 50

between the transferred linear DNA & the circular chromosome of the recipient (Hfr gene transfer)

Question 51

what produces partial diploids?

Answer 51

F'

Question 52

what is derived from the abberant excision of the F factor from an Hfr chromosome?

Answer 52

an F' donor bacterium that contains a functional F factor

Question 53

what does the F' factor contain

Answer 53

all its own DNA plus a segment of the bacterial chromosome

Question 54

what are donor cells carrying an F factor called?

Answer 54

F' cells

Question 55

exconjugants that contain a complete F' factor called what & why?

Answer 55

partial diploids since they contain two copies of the bacterial chromosome genes found on the F' factor

Question 56

is the partial diploidy retained as a characteristc of the exconjugants & their descendants?

Answer 56

`yes

Question 57

what is a merozygote

Answer 57

a state when a partially diploid bacterial cell is produced

Question 58

what can partial diploids be used to do?

Answer 58

examine the mode of action of bacterial genes & their regulation