Please enable JavaScript.
Coggle requires JavaScript to display documents.
CHAP 19 Viruses (19.2- Viruses replicate only in host cells (Viral Genetic…
CHAP 19 Viruses
19.2- Viruses replicate only in host cells
Host range- each particular virus can infect cells of only a limited number of host species
Lytic cycle- A phage replicative cycle that culminates in death of the host cell
The Lysogenic Cycle
Lysogenic cycle- allows replication of the phage genome without destroying the host
Temperate phages- Phages capable of using both modes of replicating within bacterium
Prophage- when it integrates into the bacterial chromosome
Bacterial Defenses against phages
Restriction enzymes- so named because they restrict a phage's ability to replicate within the bacterium
Viral Genetic Material
Retroviruses- RNA animal viruses have the most complicated replicative cycles.
Reverse transcriptase- an enzyme that transcribes an RNA template into DNA, RNA --> DNA information flow that is in the opposite of the usual direction
Retro viruses shown in figure 19.1
HIV (Human immunodeficiency virus)- and other retroviruses are enveloped viruses that contain two identical molecules of single-stranded RNA and two molecules of reverse transcriptase
AIDS (Acquired immunodeficiency syndrome)
Provirus- integrated viral DNA, never leaves the hosts genome, remaining a permanent resident of the cell
19.3- Viruses and prions are formidable pathogens in animals and plants
vaccine- is a harmless derivative of a pathogen that stimulates the immune system to mount defenses against harmful pathogen.
Emerging viruses
Epidemic- widespread outbreak
Pandemic- a global widespread outbreak
Prions: Proteins as Infectious Agents
Prions- proteins, appear to cause a number of degenerative brain diseases in various animal species
figure 19.13
A Borrowed Life:
Virus- is an infectious particle consisting of little more than genes packaged in a protein coat
19.1- A virus consists of a nucleic acid surrounded by a protein coat
Capsids & Envelopes:
Capsid- the protein shell enclosing the viral genome
Viral envelopes- which are derived from the membranes of host cell, contain host cell phospholipids & membrane proteins. and also contain proteins & glycoproteins or viral origin.
Bacteriophages- complex capsids, viruses that infect bacteria or (phages).