lytic cycle

11
Virus Replication

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Page 1: Lytic cycle

Virus Replication

Page 2: Lytic cycle

• 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?

Page 3: Lytic cycle

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

Page 4: Lytic cycle

• 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?

Page 5: Lytic cycle

• 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

Page 6: Lytic cycle

• 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

Page 7: Lytic cycle

• 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

Page 8: Lytic cycle

• 2nd Step: Entry– Virus enzyme weakens cell membrane– Genetic material (DNA or RNA) enters host cell

The Lytic CycleThe Lytic Cycle

endocytosis

Page 9: Lytic cycle

• 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

Page 10: Lytic cycle

• 4th Step: Assembly (formation)– New virus parts

are assembled in the cytoplasm

The Lytic CycleThe Lytic Cycle

Page 11: 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