1. Animal viruses/other infectious agents.
Medgar Evers College
Dr. Santos

2. Animal viruses are divided into a number of families, whose name end in –viridae.
Examples of RNA and DNA animal viruses that infect vertebrates are

3. RNA viruses 1- picornaviradae 8- paramyxoviridae
2-caliciviridae orthomyxoviridae
3-togaviridae bunyaviridae
4- flaviviridae arenaviridae
5-coronaviridae reoviridae
6-rhabdoviridae birnaviridae
7- filoviridae retroviridae

4. DNA viruses 1- hepadnaviridae 2- parvoviridae 3-papillomaviridae
4-polyomaviridae
5- adenoviridae
6- herpesviridae
7- poxviridae

5. Reproductive cycle of animal viruses involved in infections
Steps are
1- attachment
2- penetration and uncoating
3- synthesis of protein and replication of nucleic acid
4- assembly
5- release

6. Attachment
Many glycoprotein receptors are on the surface of the cell membrane to which the viral attachment proteins will bind to.
Example. HIV must bind to 2 key molecules on the cell surface before it can enter the cell. These are CCR5 and CD4 receptors.

7. Penetration and uncoating
Naked viruses
the virus enters by the process of endocytosis in which the cell membrane surrounds the viral particle and forms a vesicle. After being engulfed, the virus dissolves the vesicle and its released into the cytoplasm.

8. Enveloped viruses can enter the host by one of two mechanisms;
1-Fusion with the host membrane
2- Endocytosis

9. Entry following membrane fusion
The envelope of the virus fuses with the cell membrane after attachment to a host cell receptor. This is enhanced by fusion proteins on the surface of the virus.
Following fusion, the nucleocapsid is released directly into the cytoplasm.
The nucleic acid separates from the protein coat.

10. Entry by endocytosis
The host plasma membrane surrounds the whole virion and forms a vesicle.
The envelope of the virion then fuses with the plasma membrane of vesicle.
Nucleocapsid is released.
Separation of nucleic acid from the capsid.

11. Nucleic acid replication/protein synthesis
Involves transcription or the production of messenger RNA from either DNA or RNA.

12. Assembly
The capsids and genome are assembled together.
Most RNA viruses are assembled in the cytoplasm while most DNA viruses are put together in the nucleus.

13. Release
Enveloped viruses- budding
Naked virus- are released when cell dies due to the virus triggering apoptosis