ssRNA Single-Stranded RNA

Either top-strand (plus strand) or bottom strand (negative strand).

Human RNA uses plus strand RNA, so any negative strand has to be duplicated into it's sister, plus strand, using specific enzymes in order to be read by the host cell's ribosomes.

dsDNA Double-Stranded DNA

Like human DNA.

Viruses Are Diverse

Genes are highly diverse.

Genomes are generally very small.

Have multiple strains: rapid mutations/evolution.

Examples of Viruses

Influenza, Coronavirus, HIV, Herpes, Bacteriophages, Mimivirus.

Symptoms/Diseases Associated with Viruses

Polio, Smallpox, Chickenpox, Rabies, Tobacco Mosaic Virus, Zikavirus, Tulip Breaking Virus.

Structure of Viruses

Capsid

Outer protein coats surrounding nucleic acids.

Enveloped Virus

These have a capsid inside the lipid membrane.

Has a lipid membrane outer coating that is taken off of the host cell.

• Susceptible to detergents.

• Required for infectivity, spike proteins exist on the lipid membrane.

• "Hides" virions from the immune system.

Non-Enveloped Virus

Outer-capsid only.

"Naked"

More hearty.

Resistant to detergents.

Spike proteins exist on the outer capsid.

Types of Viruses

ssRNA Viruses

Influenza

• Has 8 -ssRNAs.
• mRNAs re-assort in the host cell creating genetic diversity.
• Needs viral RdRp (rna-dependent RNA polymerase).
  • Converts the negative virus RNA into positive RNA that the host can read and replicate.
• Many types of H and N proteins define virulence.

  • H1N1, H2N3, H7N9

  • H stands for Hemaglutinin, helps infect.
  • N stands for Neuraminidate, helps escape (spread).

Strains

A

B

C

D

Different types of in the same cell may mix and match genes when they re-package themselves.

Viruses can swap genes!

Coronavirus

• Single +ssRNA

dsRNA Viruses

• Two non-enveloped capsids. An inner capsid and an outer capsid.
• Replicates inside the inner capsid to evade defenses.
• Needs RdRp to make RNAs.

dsDNA Bacteriophages Infect Prokaryotes

• Non-enveloped, protein capsid head.
• Phages kill bacteria, as bacteria evolve more resistance to antibiotics, phages also evolve and can kill them.
• Turns to circular DNA in host cell
  • Rolling circle replication.

dsDNA HSV

_Herpes Simplex Virus

• Doesn't integrate into the host genome.

dsDNA HPV

_Human Papilloma Virus

• Can integrate into the host cell's genome.
  • Causes cervical cancer, degrades tumor-suppressing proteins.

Giant dsDNA Viruses

• Have very large genomes comparatively.

Retroviruses

• Has viral Reverse Transcriptase (RT).
• Integrates into the host genome.
• Difficult to get rid of (HIV).

Vaccines

mRNA Vaccines

Teaches cells to build the spike proteins used by viruses that your immune system can then recognize before encountering the real virus.

Does your immune system kill your cells that made the spike protein that your immune system doesn't recognize?

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