lytic cycle
DESCRIPTION
TRANSCRIPT
Virus Replication
• Virus: A biological particle composed of nucleic acid and protein
• Intracellular Parasites: organism that must “live” inside a host
What is a Virus?What is a Virus?
Is Fire Alive?Is Fire Alive?
• 1) Made of cells?• 2) Organization?• 3) Require energy?• 4) Respond to Environment?• 5) Grow?• 6) Reproduce?• 7) Adapt?
yes
yes
yes
yes
no
no
no
• Reproduce• They have DNA or
RNA• They can adapt to
surroundings• The have
organization
• They are not made of cells or organelles
• They cannot reproduce without a host
• They don’t have both DNA and RNA (RNA is a single strand of
DNA that has been copied. RNA is used to tell your body what proteins and enzymes to make, along with which genetic codes to activate.)
• They do not metabolize energy
YesYesNoNoAre Viruses Alive?Are Viruses Alive?
• All Have:– 1) Capsid: coat of
protein that surrounds DNA or RNA
– 2) Nucleic Acid: RNA or DNA
• Some Have:– Tail Fibers: Used for
attachment (not legs)• Shapes vary
Virus PartsVirus Parts
• Cannot reproduce w/o a host cell– Virulent: cause disease
• Bacteriophages (infect bacteria) are often studied– Replication is similar with many animal
viruses
Viral ReplicationViral Replication
• 1st Step: Attachment– Virus lands on cell
membrane– Virus attaches to a
cell receptor– No attachment = No
infection– Virus acts as a “key”
to the receptor
The Lytic CycleThe Lytic Cycle
• 2nd Step: Entry– Virus enzyme weakens cell membrane– Genetic material (DNA or RNA) enters host cell
The Lytic CycleThe Lytic Cycle
endocytosis
• 3rd Step: Replication– Virus DNA/RNA uses
ribosomes to make virus proteins
– Proteins created by transcription/translation
– Virus proteins make new virus parts
The Lytic CycleThe Lytic Cycle
• 4th Step: Assembly (formation)– New virus parts
are assembled in the cytoplasm
The Lytic CycleThe Lytic Cycle
• 5th Step: Lysis & Release– Virus enzyme causes cell membrane to “lyse”– New viruses are released to find new host– Cycle repeats
The Lytic CycleThe Lytic Cycle