Final Exam Flashcards
Prophage
Phage DNA incorporated at specific position within host cell DNA; becomes part of the bacterial DNA
Lysogenic cell ( lysogen)
Are Prophage carrier cells
Phage induction
When the Prophage “ switches” from latent infection to lyric pathway
Lysogenic conversion
When Prophage brings some new trait to the host cell.
Mini virus
Largest virus infects ameba almost mimics a bacteria cell.
Picorna Virus
A virus belonging to the family picornaviridae. Is a family of viruses in the order picornsvirales, vertebrates, including humans, serve as nateral hosts.
Small pox
Is an infectious disease caused by either of two virus variants.
How does a virus differ from a cell
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
Helical
Rod shaped
Rabies, SARS cornia virus
Icosahedral shape
Spherical appearance
Papillomavirus (HPV)
Picornsvirus (polio, HRV)
Phage structure
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
Steps of replication
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.
Late proteins
Capsid proteins (capsomers)
Lysozyme- made later time/ late proteins.
B. Replication of Phage DNA-
Phage protein sythesis and DNA replication occurs independly.
Scaffold proteins
Are used to provide the platform in which the assembly occurs/ made later, does not become apart of virus structure.
Picornavirus
Polio
Small,
Non enveloped
Positive sense RNA
HIV
Capsid, glycoprotein
Identical RNA strand
Reverse transcriptase enzyme
Rabies
Helical
Viral disease that causes acute inflammation of the brain
HRV
Pocornaviruses
Rhino virus
Lytic pathway
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.
5 stage
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.
Lysozyme
A protein enzyme carried with in the capsid that weakens the peptidoglycan of the cell wall.
Prophage
Phage DNA incorporated at specific position with in host cell DNA, become part of the bacterial DNA.
Provirus
Some animal viruses, including chicken pox and herpes virus may remain dormant in cells in a process called latency.
Temperate phage
Phage that live in close relationship with host bacterial cells.
Lysogenic conversion
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
Lysogenic conversion
Lysigenic phages ca change the phenotype of a bacterium for example from a harmless form into a pathogen- a process called lysogenic conversion.
Prophage
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.
Provirus
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.
Defective phage
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.
Transduction concept
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.
Burst
For any phage undergoing Turkic replication the period of time required to complete.
Bust size
And number of new virons released from each loses becerial cell is called the burst size.
Phage induction
At some later time a Prophage might be excised from the chromosome by recombination
Or some genetic event
It re- enters the Lytic phase.
Temperate phage
Phage that live in close relationship with host bacterial cells.
