Transcript VIRUSES - Norman Public Schools

Viruses
VIRUSES: General Information
• Non Living
• Contains a Caspid: Protein coat
surrounding it.
• Core is composed of either DNA or
RNA.
DNA VIRUSES
• Contains either single strand or
double strand of DNA
• Virus inserts the viral DNA into host
cell.
• Occurs in the nucleus.
VIRAL DNA REPLICATION
• Cell Divides and viral DNA is
replicated.
• Viral DNA is produced every
time the cell divides
VIRAL DNA REPLICATION
• Viral mRNA leaves the
nucleus
• Attaches to Ribosome's
• Viral proteins are produced.
RNA VIRUSES
• Examples: Polio and Tobacco
Mosaic Viruses.
• Viral RNA enters the cell and
travels directly to the
ribosome.
• Makes viral proteins.
RETROVIRUS
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Enters the cell as RNA
Travels to the nucleus
Converts viral RNA to viral DNA
Uses Reverse Transcriptase
Viral DNA inserts itself into the
actual chromosomes of the host
organism. (Provirus)
RETROVIRUS
(backwards virus / HIV)
• The viral DNA is then replicated
with the normal DNA
• The cell now produces viral
RNA to and makes viral
proteins.
RETROVIRUS
• Example: HIV
• HIV replicates very quickly
• Takes over the cell
• Mutates rapidly
• Difficult to make a vaccine.
1. Attachment:
Virus attaches to
host cell
Lytic Cycle
2. Entry:
Nucleic Acid is
injected into the
cell
5. Lysis and
Release: Host cell
breaks open and
new viruse are
released.
3. Replication:
Viral DNA is
replicated
4. Assembly:
New virus
particles are
assembled
Lysogenic Cycle
• Viral DNA becomes a part of the host cells
chromosomes (provirus)
• The virus is inactive but still replicates with
the normal DNA.
• Continues to replicated until it decides to
enter the Lytic Cycle.
• The virus will leave the host chromosomes
and then undergoes Lytic Cycle.
Comparison of Lytic and
Lysogenic Cycles of Viruses