microbial genetics

Question 1

what is horizontal gene transfer

Answer 1

genes are passed laterally from one mature prokaryote to another

Question 2

what type of organisms can undergo HGT

Answer 2

prokaryotes

Question 3

what is a recombinant organism

Answer 3

one that has characteristics of both the donor and recipient

Question 4

what is the main method of genetic diversity among prokaryotes

Answer 4

HGT

Question 5

what types of DNA can be transferred in HGT

Answer 5

a DNA fragment or a plasmid

Question 6

list the 3 methods in which HGT can occur

Answer 6

conjugation, transformation, transduction

Question 7

what are the 2 possible fates for HGT

Answer 7

either you get stable recombinants or no stable recombinants

Question 8

what 2 ways can we get stable recombinants due to HGT

Answer 8

if the DNA is integrated into the host chromosome or if the donor DNA self replicates into a plasmid

Question 9

what 2 ways do we get no stable recombinants due to HGT

Answer 9

when the donor DNA cannot self replicate, or when there’s degradation of donor DNA

Question 10

define conjugation

Answer 10

transfer of genetic material from a donor cell to a recipient cell via direct contact

Question 11

what is conjugation mediated by

Answer 11

the F plasmid

Question 12

what does the F plasmid stand for

Answer 12

fertility plasmid

Question 13

how many stands do plasmids have

Answer 13

2

Question 14

shape of plasmids?

Answer 14

linear or circular

Question 15

do plasmids have lots of few genes

Answer 15

few

Question 16

describe the importance of plasmids in regards to the host genome

Answer 16

plasmids are seen as “extra” for the host

Question 17

describe the number of copies that plasmids can exist as

Answer 17

can be single or multicopy

Question 18

define episome

Answer 18

a plasmid that can exist with or without being incorporated into the host’s chromosome

Question 19

T or F: the F plasmid is an episome

Answer 19

true

Question 20

what are cells that carry the F plasmid called

Answer 20

F+ (donor)

Question 21

what are cells that lack the F plasmid called

Answer 21

F- (recipient)

Question 22

what do F+ cells produce to aid in conjugation

Answer 22

sex pili

Question 23

what type of bacteria is the F plasmid found in

Answer 23

only gram negative

Question 24

T or F: the F plasmid is found in all types of bacteria (both gram neg and pos)

Answer 24

false; only gram negative

Question 25

describe conjugation briefly

Answer 25

donor cell protrudes the sex pilus and contact is made with the recipient cell. F plasmid goes through the sex pilus into the recipient cell and then the pilus retracts

Question 26

in terms of F+ and F-, describe the final result of an F+ cell conjugating with an F- cell

Answer 26

both cells become F+

Question 27

describe how the F plasmid can be incorporated onto the recipient's chromosome

Answer 27

plasmid contains sequences that are homologous to sequences on the chromosome, thus homologous recombination can occur (plasmid insertion)

Question 28

what is homologous recombination

Answer 28

plasmid integrates into the host's chromosome due to homologous sequences

Question 29

what is an Hfr cell (how is it made)

Answer 29

made when a bacterium gets the F plasmid integrated into it's chromosome

Question 30

where is the plasmid DNA from the donor located in an Hfr cell

Answer 30

plasmid DNA has been incorporated into the chromosome

Question 31

what does Hfr stand for

Answer 31

high frequency of recombination

Question 32

what happens when an Hfr cell and F- cell conjugate

Answer 32

the chromosome breaks before the entire thing has transferred and the F plasmid is not transferred. F- remains as such, though it can contain new chromosomal genes

Question 33

result of Hfr x F-

Answer 33

Hfr and F-

Question 34

T or F: an integrated F plasmid may hop out of the Hfr chromosome

Answer 34

true

Question 35

what can happen when the integrated F plasmid hops out of the Hfr chromosome

Answer 35

a mistake in excision may occur, and it may carry some of the donor's chromosomal genes with it

Question 36

what is produced when the integrated F plasmid leaves the Hfr chromosome + takes donor genes with it

Answer 36

we get F' (F prime)

Question 37

what do we get when F' x F-

Answer 37

F' and F'

Question 38

T or F: conjugation can occur in both gram neg and gram pos bacteria

Answer 38

true; but there are some differences

Question 39

list 1 difference in gram pos conjugation vs gram neg conjugation

Answer 39

gram pos conjugation does not involve a sex pilus

Question 40

define transformation

Answer 40

the uptake of DNA from the environment

Question 41

what two forms of DNA can be used in transformation

Answer 41

DNA fragment or a plasmid

Question 42

what are competent cells

Answer 42

a cell that's in a physiological state in which it can uptake donor DNA

Question 43

in what environments might transformation occur (4)

Answer 43

soil, water, in vivo, biofilms

Question 44

how does transformation work

Answer 44

a pilus extends into the environment and retracts back into the cell when it contacts DNA

Question 45

are E coli cells naturally competent

Answer 45

no

Question 46

how are e coli cells made competent in the lab

Answer 46

heat shock with CaCl or electrical shock via an electroporator

Question 47

define transduction

Answer 47

the mechanism by which bacterial genes are transferred from one bacterium to another via a bacteriophage

Question 48

what are bacteriophages

Answer 48

viruses that infect bacteria

Question 49

list the 2 types of bacteriophages

Answer 49

virulent or temperate

Question 50

what do virulent phages do/what do they do to the bacteria

Answer 50

they lyse the bacterial cell

Question 51

what do temperate phages do/what do they do to the bacteria

Answer 51

1. can reproduce lytically 2. can integrate into the host's chromosome + remain with it without destroying the bacterial cell

Question 52

what is the viral genome called once the temperate phage has integrated into the host's chromosome

Answer 52

prophage

Question 53

what is the name for the bacterium that's harboring the temperate phage

Answer 53

lysogen

Question 54

go through the steps of the lytic cycle

Answer 54

phage injects DNA into host cell's cytoplasm. This directs the synthesis of many new phages, then cell lyses and releases the new pathogens/phages. the phages can then bind to other cells

Question 55

go through the steps of the lysogenic cycle

Answer 55

phage injects DNA into cell and then the DNA is integrated into the host chromosome. Prophage DNA is copied when the cell divides. Exposure to stress (ie UV light) triggers excision from the host chromosome, and now the host chromosome is pure again

Question 56

what temperate phage infects e coli

Answer 56

bacteriophage lambda

Question 57

what are the two types of transduction

Answer 57

general and specialized

Question 58

when does general transduction occur (what cycle)

Answer 58

during the lytic cycle

Question 59

what types of phages use general transduction

Answer 59

both virulent and temperate

Question 60

describe general transduction

Answer 60

random pieces of DNA are transferred from one bacterium to another via a phage. Any piece of the host's chromosome can be transferred = generalized

Question 61

when does specialized transduction occur

Answer 61

when there is an error in the life cycle of a temperate phage

Question 62

why is specific transduction called specific

Answer 62

only specific pieces of DNA from the host will be transferred to the recipient via a phage

Question 63

describe how HGT can be responsible for the spread of antibiotic resistance

Answer 63

microbes that synthesize antibiotics must have resistance genes. these genes are spread via HGT to other cells, giving them resistance too. OR spontaneous mutations may occur but less likely