Virus - Latin name for poison

Characteristics Does not fit in the 6 kingdom classification system A chemical that carries out no life function of its own Invades a living/host cell; displays a trait that is shared with all living things: Reproduction

Cont’d nm (nanometre=1 billionth of a metre) Less complex than simple organisms Nucleic acid core contains only DNA OR RNA. – Not both, unlike other living organisms

Bacteriophages are a category of viruses that infect bacteria (eaters of bacteria) – Outer protective protein coat (Capsid) – Inner nucleic acid core

Viral Diversity Viruses must enter cells to carry out life processes – not all are considered disease causing agents or pathogens Selective to specific host cells First viruses discovered infected higher plants and animals Bacteriophages were discovered in 1940 – they have been the main experimental subject for examining biological properties of viruses

Viral Specificity Highly specialized relationship with host – Only plants OR animals OR bacteria Host Range: the limited number of host species or cells that a virus or parasite can infect Bacteria – restricted host range Animals – broad host range Plants – very wide host range

Viral Replication Replication: process where genetic material is duplicated before the cell divides 1) Attachment: recognizes a host cell and attaches to it 2)Synthesis: of protein and nucleic acid. Molecular information in the DNA/RNA directs host cell in replicating components of the virus 3) Assembly: viral components are put together, making new virus particles 4) Release: new virus particles are released and the host cell dies ^^^^^^^^^^LYTIC CYCLE^^^^^^^^^

Cont’d minutes results in 300 new virus particles Lysogenic cycle: – does not kill the host cell – nucleic acid is injected into DNA/RNA of host cell – replicated with the host cell’s DNA acting as another set of genes on the host chromosome – DNA is then passed along to daughter cells In a dormant state, until it is activated by a stimulus and the cycle becomes lytic again (ex. Cancer-causing virus)

Human Health As the virus reproduces it attacks the host cell, this damage to the cells is what causes the symptoms of a disease Vaccination: solutions that are prepared from viral components or inactivated viruses As if the body was infected with the real virus – produces antibodies – antibodies stay with us – we are then immune to that specific disease

Any Question?

Activity Draw a picture of your own made up virus. Be creative! – Include a description of what its host is and what kind of effect it has on it – Label the outer protective protein coat (Capsid) and the inner nucleic acid core Page 338 #1-6 and 8