Bacteriophages

Question 1

What are the 4 types of phage classification

Answer 1

Ds dna

Ss dna

Ss rna

Ds rna

Question 2

What happens to dna if it’s ssdna

Answer 2

Replicated then converted to mrna +

Question 3

Name a ss dna phage

Answer 3

M 13

Question 4

Why wouldn’t M13 ds dna show up as a PFU

Answer 4

Has no cytopathic effects

It is released without lysis

Question 5

What is ss dna phages like M13 used for and why

Answer 5

Gene cloning as vectors

They have space in genome for the gene of interest

Question 6

what is phage displaying usually done on ss dna like M13

Answer 6

It is insertion of the gene (cloning) to detect its function when infecting bacteria

Question 7

Which phage is most common and give example

Answer 7

Ds dna

Eg T4

Question 8

What is the advantage of SSRNA (+)

Answer 8

It doesn’t have to be converted to mrna as already sense

It can be translated straight away

Question 9

What do Ss rna (-) phages use (different in viruses)

Answer 9

Use rna replicase converting it to + mrna

Question 10

What allows a phage to attach

Answer 10

Tail fibres

Question 11

Which enzymes allow entry into the bacteria and also exit

Answer 11

Lysozymes

Question 12

What allows injection of nucleic acid into bacteria

Answer 12

Receptor recognising the phage

Question 13

Which period can’t detect phage in it outside of the cell

Answer 13

Eclipse period

Question 14

What is the lag phase in phage graphs

Answer 14

The bottom line

It is the period where the maturation of virion occur before lysing

Question 15

What is the rise period

Answer 15

The exponential growth where the phage has lysed

Shown on graph

Question 16

At what phase do PFU stop increasing (after rise period)

Answer 16

Plateau period

Question 17

What is the name for number of phages released from 1 cell

Answer 17

Burst size

Question 18

How do you work out burst size

Answer 18

PFU highest value / PFU lowest value

Question 19

Are T4 ds dna phages lytic?

Answer 19

Yes

Question 20

What happens to all of the dna when injected

Answer 20

Both host and phage dna are hydrolysed before assembly

Question 21

At what point does lysozyme production occur/ translation/ assembly

Answer 21

At the exponential phase - causes lysis

Question 22

What is the main lysogenic phage called

Answer 22

Lamda

Question 23

What are lysogenic lamda phages good for

Answer 23

Transfer pathogenic/ virulence to the bacteria chromosome

Question 24

What is it called when the lysogenic lamda genome is incorporated to host chromosome

Answer 24

PROPHAGE

Question 25

What is a lysogen

Answer 25

Phage which dna is replicated within the host chromosome as a prophage

Question 26

Which protein in high numbers causes flip to the lysogenic phase

Answer 26

Cl protein

Question 27

Which protein causes a flip to the lytic cycle

Answer 27

Cro protein

Question 28

When would lysogenic cycle be favoured

Answer 28

If bacteria are in harsh conditions and not likely survive

Question 29

Why can lamda phages be used for cloning alongside M13 (ss dna)

Answer 29

1/3 of its genome can be replaced with a gene of interest

Question 30

Why is T7 used for cloning

Answer 30

They have a specific T7 rna polymerase which only works alongside specific promoters

Used for manipulating expression of genes

Question 31

Why can phages be used as alternative to antibiotics

Answer 31

Kill bacteria (phage therapy)

And useful in stopping biofilms eg in toothpaste