Final Exam

Question 1

Prophage

Answer 1

Phage DNA incorporated at specific position within host cell DNA; becomes part of the bacterial DNA

Question 2

Lysogenic cell ( lysogen)

Answer 2

Are Prophage carrier cells

Question 3

Phage induction

Answer 3

When the Prophage “ switches” from latent infection to lyric pathway

Question 4

Lysogenic conversion

Answer 4

When Prophage brings some new trait to the host cell.

Question 5

Mini virus

Answer 5

Largest virus infects ameba almost mimics a bacteria cell.

Question 6

Picorna Virus

Answer 6

A virus belonging to the family picornaviridae. Is a family of viruses in the order picornsvirales, vertebrates, including humans, serve as nateral hosts.

Question 7

Small pox

Answer 7

Is an infectious disease caused by either of two virus variants.

Question 8

How does a virus differ from a cell

Answer 8

Viruses are not considered living cells. They are not able to alive unless they are in a host. Then they can reproduce using the host cell genetic material and mechanisms. If not then when outside host cells, viruses exist as a protein coat or capsid, sometimes enclosed with in a membrane.

While outside the cell, the virus is matabically inert. While a bacteria who are pathogenic can still be alive outside a host cell and contain metabolic activity.

Viruses have no fossil

Question 9

Helical

Answer 9

Rod shaped

Rabies, SARS cornia virus

Question 10

Icosahedral shape

Answer 10

Spherical appearance

Papillomavirus (HPV)

Picornsvirus (polio, HRV)

Question 11

Phage structure

Answer 11

Head:isometric shape

Tail: comprised of distinct parts:
Collar, sheath, contractile surrounds hollow tube.

Base plate: Tail pin spikes
Tail fibers ( protein)

Phage genome:

• d’s DNA
• s’s DNA
• s’s RNA

Question 12

Steps of replication

Answer 12

Attachment-
Weak interaction between tip of tail fibers ( attachment proteins)
And specific residues ( receptors) on the cell surface.

Tail pins on the base plate reinforces the attachment step

Entry-
Seperation of capsid protein and necleic acid

Lysozyme degrades cell wall

Lysozyme activation following attachment step results in:

1- compression of tail contrastive sheath units
2-tube penetrates through cell wall and membrane, tip opens and phage DNA slips through into cytoplasm.

Synthesis:

Includes genome replication transcription and translation. Incoming phage DNA transcribed and translated into proteins.

Transcription and translation

Assembly:
Complex multi step, orderly sequence of events self essemby, non enzymatic process.

Involves capsid and phage DNA interaction to form mature infective phage.

Release: lysozyme is synthesized during the later stages of productive infection.
- lysozyme breaks cell wall from inside a cell lysis ensues.

Question 13

Late proteins

Answer 13

Capsid proteins (capsomers)

Lysozyme- made later time/ late proteins.

B. Replication of Phage DNA-
Phage protein sythesis and DNA replication occurs independly.

Question 14

Scaffold proteins

Answer 14

Are used to provide the platform in which the assembly occurs/ made later, does not become apart of virus structure.

Question 15

Picornavirus

Answer 15

Polio
Small,
Non enveloped

Positive sense RNA

Question 16

HIV

Answer 16

Capsid, glycoprotein
Identical RNA strand

Reverse transcriptase enzyme

Question 17

Rabies

Answer 17

Helical

Viral disease that causes acute inflammation of the brain

Question 18

HRV

Answer 18

Pocornaviruses

Rhino virus

Question 19

Lytic pathway

Answer 19

The Lytic cycle is one of two cycles of viral production

The other being lysogenic cycle

Results in the destruction of the infected cell and its membrane.

A key difference is that in the Lytic phage the viral DNA exists as a separate molecule with in the bacterial cell, and replicates seperatly.

In the Lytic phage cycle, the phage is a free floating separate molecule to the host DNA.

Question 20

5 stage

Answer 20

Attachment- of the viron to the host cell

Entry- of the viron or its genome into the cell.

Synthesis- of the new necleic acids and viral proteins by the host cell’s enzymes and ribosomes.

Assembly- of new virons

Release- of the new virons from the host cell.

Question 21

Lysozyme

Answer 21

A protein enzyme carried with in the capsid that weakens the peptidoglycan of the cell wall.

Question 22

Prophage

Answer 22

Phage DNA incorporated at specific position with in host cell DNA, become part of the bacterial DNA.

Question 23

Provirus

Answer 23

Some animal viruses, including chicken pox and herpes virus may remain dormant in cells in a process called latency.

Question 24

Temperate phage

Answer 24

Phage that live in close relationship with host bacterial cells.

Question 25

Lysogenic conversion

Answer 25

Bacteriophage genes are responsible for toxins and other disease- envoking proteins found in the bacterial agents of Diptheria, cholera, rheumatic fever and certain severe cases of diarrhea cause by e, coli

Question 26

Lysogenic conversion

Answer 26

Lysigenic phages ca change the phenotype of a bacterium for example from a harmless form into a pathogen- a process called lysogenic conversion.

Question 27

Prophage

Answer 27

Remains inactive by coding for a protein that supresses Prophage genes. A side affect of this repressor protein is that it renders the bacterium resistant to additional infection by other viruses of the same type.

Question 28

Provirus

Answer 28

Remain dormant in cells in a process known at latency or pro viruses

Some latent viruses do not become incorporated into the chromosomes of their host cells/ where as lysogenic phages always do.

HIV- are more like lysogenic phages in that they do become inter graded into a host chromosome as a virus.

Question 29

Defective phage

Answer 29

A temperate bacteriophage mutant with a genome that does not contain all normal components and cannot become fully infectious virus, yet can replicate indefinitely in the bacterial genome as defective bacteriophages are mediators of transduction.

Question 30

Transduction concept

Answer 30

A process of genetic recombination in bacteria in genes from a host cell( s bacterium) are incorporated into the genome of a bacterial viruses( bacteriophage)

And then carried to another host cell when the bacteriophage initates another cycle of infection.

Question 31

Burst

Answer 31

For any phage undergoing Turkic replication the period of time required to complete.

Question 32

Bust size

Answer 32

And number of new virons released from each loses becerial cell is called the burst size.

Question 33

Phage induction

Answer 33

At some later time a Prophage might be excised from the chromosome by recombination
Or some genetic event

It re- enters the Lytic phase.

Question 34

Temperate phage

Answer 34

Phage that live in close relationship with host bacterial cells.