Animal Viruses
• Transcription in the prokaryotes and translation in the cytoplasm Transcription in the eukaryotes occurs in the translation of the nucleus in the cytoplasm.
• In eukaryotes, the mRNA is processed, the 3 ’end is bound to Poly-A, and the 5’ end is bound to the cap (methyl guanosine triphosphate) required for binding of the mRNA to the ribosome.
• In prokaryotes, mRNA is polysistronic and monocistronic in eukaryotes.
• In prokaryotes, the penetration of viruses through a hard cell wall made of peptidoglycan differs from the penetration of viruses into animal cells without cell walls.
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The proliferation of animal viruses occurs in four ways.•
In abortive infections where the virus cannot complete replication, some viruses producetumors (transformation).
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Some tumors do not spread to the body (benign, benign tumor), some tumors (malignant,malignant) spread in the body. metastasized
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Infections resulting in reproduction:•
Limiting infections:•
Latent infections:How does a normal cell become cancer cell?
Cell growth is controlled by protooncogen and tumor suppressor gene.
Protooncogenes allow proliferation, tumor suppressor genes control proliferation.
Changes in these genes cause cancer. These changes in the cell are caused by some chemicals called
carcinogens, UV or X rays and some viruses.
The protooncogene is translated into the oncogene forming tumor.
Damages caused by animal viruses to their hosts
Inhibits DNA, RNA and protein synthesis of the host cell
As a result of the damage to the lysosomes, the hydrolytic enzymes in them spread out into the cell and break down the cell.
As a result of viral infection, viral proteins are inserted into the membrane of the host cell and the structure of the cell
membrane changes and these cells are destroyed by the immune system.
High concentration of viral protein in the cell has a direct toxic effect on the cell.
Inclusion bodies seen as a result of the accumulation of virions in the cytoplasm or nucleus where the viruses are packaged directly damage the cell structure.
As a result of infection of some viruses, chromosomes in the cell are damaged by the integration of viral genome.
The host is not directly damaged, but by transformation the cell is transformed into a tumor cell.
Norovirus “ norwalk like virus”
In humans, it causes an infectious disease that causes nausea, vomiting, diarrhea fever and headache in the digestive tract (stomach and intestines).
Outbreaks; luxury restaurants, hotels and entertainment venues
After 24-48 hours in patients receiving Norovirus; severe
nausea, vomiting, diarrhea, sometimes headache and fever.
The disease spontaneously resolves within 2-3 days.
The disease is transmitted to healthy people by ingestion of the causative agent. It is transmitted to people who drink contaminated food and drinks.
It is also transmitted from sick people to people in contact with their interests.
RNA VIRUSES
Negative sense RNA virüses
Rabies virus, Rhabdoviruses,
Mumps and Measles virus Paramyxoviruses Flu (influenza) virus, Orthomyxoviruses
All viruses in this group are sheathed and carry enzymes in their virions.
• Influenza virus
• Helical nucleocapsid 8 linear (-) ssRNA molecules,
• RNA polymerase and RNA endonuclease enzyme
• They contain hemaglutinin and neuraminidase enzyme.
• 10 proteins from 8 mRNAs
• Antigenic shift
• Antigenic drift
C. Double-stranded RNA viruses- Reoviruses
Polyhedral virions have enzymes and linear ds RNA segments of 10-12 molecules.
Replication occurs in the cytoplasm. mRNAs are transcribed from viral genome
segments with viral enzymes. Negative strand RNAs are then synthesized using
these as molds. By converting them into a double-stranded form, new virus nucleic
acids are synthesized. In the cytoplasm, the genome segments are then packaged
within the capsule.
DNA VIRUSES
1. Papovaviruses: Simian virus 40 (SV40)
2. Herpesviruses:
3. Pox viruses:
4. Adenoviruses:
3. Pox viruses:
Linear dsDNAs are fairly large viruses of 200-400 nm length replicating in the host cell cytoplasm. Smallpox virus is found in this group. Virions are covered with a sheath of protein rather than lipid. There are two lateral structures consisting of lipid and protein between the
nucleoid regions and outer membranes where their DNA is located.
Some viruses in this group (vaccinia virus used in vaccine production) are used in gene engineering studies,
because they are not pathogenic to humans, to introduce foreign genes into animal or human cells.
4. Adenoviruses:
They are commonly found in humans. These viruses,
which do not cause cancer in humans, cause infection in the upper respiratory tract, eye and digestive systems.
They cause cancer in animals. Non-sheathed polyhedral viruses. They contain linear double-stranded DNA.
