chapter 6 part 2

Question 1

transformation

Answer 1

occurs when recipient cell takes up a fragment of donor DNA from the surrounding growth medium

Question 2

is transformation naturally occurring or induced in a laboratory

Answer 2

both

Question 3

how is transformation used in the laboratory

Answer 3

to introduce DNA into microbial cells, plant cells, and animal cells

Question 4

length of transforming DNA

Answer 4

usually shorter than 100 kb
- in E. coli can contain up to 50 genes, representing at most only 1-2% of total genome of recipient

Question 5

what is transformation useful for

Answer 5

mapping genes that are closely linked

Question 6

cotransformation

Answer 6

simultaneous transformation of two or more genes

Question 7

what precedes natural transformation

Answer 7

lysis

Question 8

lysis

Answer 8

breakage of a donor cell and fragmentation of the DNA of the donor

Question 9

how many steps in transformation

Answer 9

4

Question 10

steps in natural transformation

Answer 10

• lysis
• passage of DNA into a recipient accompanied by degradation of one of the strands
• remaining strand aligns with complementary regions of the recipient chromosome
• alignment of donor/recipient DNA triggers excision of one strand of recipient DNA and replacement with donor DNA

Question 11

heteroduplex

Answer 11

when alignment of donor/recipient DNA triggers excision of one strand of recipient DNA and replacement with donor DNA

Question 12

products of transformation

Answer 12

• one daughter cell is transformed cell (transformant)
• other daughter cell retains the recipient chromosome original DNA strand (unchanged)

Question 13

transformant

Answer 13

transformed cell

Question 14

steps of lytic cycle

Answer 14

1. attachment of phage to host cell
2. injection of the phage chromosome into the host, followed by circularization of the phage chromosome
3. replication of phage DNA using host proteins and enzymes
4. transcription/translation of phage genes, production of phage components
5. packaging of phage chromosomes into phage heads
6. lysis of host cell, release of progeny phage particles

Question 15

temperate phages

Answer 15

have alternate, temporary life cycle involving integration of the page chromosome into the bacterial chromosome

Question 16

does the lysogenic or lytic cycle use temperate phages

Answer 16

lysogenic

Question 17

lysogenic cycle steps

Answer 17

1. attachment/injection same as lytic
2. integration of phage chromosome into host chromosome via recombination at specific DNA sequence found in both chromosomes
3. excision of prophage in response to an environmental signal, through reversal of site-specific recombination leading to integration
4. resumption of lytic cycle, beginning with phage-chromosome replication

Question 18

bacterial transduction mediated by bacteriophages

Answer 18

transfer of genetic material from donor to recipient by way of a bacteriophage
- phage accidentally incorporates a fragment of donor DNA rather than copy of phage chromosome

Question 19

how small are bacteriophage particles

Answer 19

less than 1% the size of the bacteria they attack

Question 20

composition of bacteriophage

Answer 20

• icosahedral head
• hollow protein sheath
• set of tail fibers

Question 21

what does the head of a bacteriophage contain

Answer 21

single chromosome from 5,000 to 100,000 base pairs

Question 22

what does replication and gene expression of bacteriophages require

Answer 22

enzymes and factors of the host cell

Question 23

what does the transfer of genetic material from a donor bacterium to a recipient via a phage lead to the production of

Answer 23

transductant bacterial strain

Question 24

2 types of transduction

Answer 24

1. generalized transduction
2. specialized transduction

Question 25

generalized transduction

Answer 25

transfer of random bacterial genes, carried out by bacteriophages that can't distinguish between phage and bacterial DNA during packing of DNA into new phage particles

Question 26

specialized transduction

Answer 26

carried out only by temperate phages and the only genes transferred are those close to the integration site

Question 27

generalized transduction steps

Answer 27

1. normal P1attaches to donor bacterium and injects DNA into the cell 2. replication of phage chromosome followed by transcription/translation to produce phage proteins 3. some phages receive host DNA fragment instead of phage DNA 4. host cell lysis releases all the progeny phages 5. generalized transducing phages attach to new recipient cells and inject DNA 6. homologous recombination may occur between donor fragment/recipient chromosome 7. stable transductant strain results

Question 28

generalized transacting phage

Answer 28

phages that receive host DNAA fragment instead of phage DNA - (random selection of DNA fragments based upon size alone)

Question 29

ex. of temperate phage

Answer 29

lambda phage

Question 30

where do lambda phages integrate into host chromosomes

Answer 30

at specific sites

Question 31

integration site in bacterial host chromosome

Answer 31

att site - same 15-bp sequence

Question 32

integration site in lambda phage

Answer 32

attP

Question 33

integration site in E. coli host

Answer 33

attB

Question 34

how similar are the attB and attP sites

Answer 34

identical

Question 35

because attB/attP are identical, excision of prophage is usually...

Answer 35

exact reversal of the integration

Question 36

possible error in excision of specialized transduction

Answer 36

only part of prophage is removed, and along with it, some of nearby bacterial DNA

Question 37

what does aberrant excision produce

Answer 37

specialized transducing phage

Question 38

what genes are found on either side of attB site in E. coli

Answer 38

galK and bioA

Question 39

(lambda)dgal+ specialized transducing phage

Answer 39

includes galK gene - can infect host cells but lacks genes needed to complete either lysis or lysogeny

Question 40

(lambda)dbio+ specialized transducing phage

Answer 40

includes bioA gene - can induce lysis but lacks genes needed for lysogeny

Question 41

lateral gene transfer

Answer 41

transfer of genetic material between ind. bacteria or archaea and other organisms

Question 42

studies suggest that more than ____% of genes in a genome are the result of LGT

Answer 42

12

Question 43

what kind of genes are more likely to undergo LGT

Answer 43

genes encoding for cell surface proteins, DNA-binding proteins, and proteins related to pathogenicity

Question 44

where does LGT occur

Answer 44

among bacteria and between bacteria and eukaryotes

Question 45

evolutionary example of LGT

Answer 45

endosymbiosis that led to mitochondria and chloroplasts in eukaryotes

Question 46

another ex. of LGT

Answer 46

LGT of 10,000-30,000 base pairs from bacterium Agrobacterium tumefaciens to plants

Question 47

how is LGT identified

Answer 47

presence of DNA-sequence features in regions of a genome that are uniquely different from the rest of the genome

Question 48

genomic islands

Answer 48

regions of genome that are uniquely dif from rest of genome

Question 49

are genomic islands usually large or small

Answer 49

large (10-200 kb) - often include multiple genes

Question 50

2 common characteristics of genomic islands

Answer 50

1. group of genes much more like genes of distantly related species than closely related species 2. ratio of G-C and A-T substantially different than rest of genome

Question 51

LGT medical importance

Answer 51

- allowed for rapid organism adaptation to changing environmental conditions by acquiring antibiotic resistance - can lead to acquired pathogenicity islands

Question 52

pathogenicity islands

Answer 52

contain genes for proteins that promote host invasion and genes that produce toxic compounds

Question 53

ex. of pathogenicity islands in certain strains of E. coli

Answer 53

can cause diarrhea and meningitis