Lecture 1-2 - Introduction to Classification & Viruses

Question 1

Mention all 7 of the taxonomic hierarchy for both plants and animals.

Answer 1

1. Kingdom
2. Phylum (Animals)/Division (Plants)
3. Class
4. Order
5. Family
6. Genus
7. Species

Question 2

What is meant by a monophyletic group?

Answer 2

A group in which all the members have a single common ancestor not shared with other species.

Question 3

Describe characteristics of a virus.

Answer 3

Virus:

• Small, range in size from 20 to 300 nm
• Obligate parasite (unculturable)
• infectious particles composed of nucleic acid and protein

Question 4

Differ between a virion, viroid, and virus.

Answer 4

Virion is the entire virus particle, which includes the capsid and the genetic material.

Viroid is a plant pathogen in the simple form of a piece of ssRNA with no capsid.

Virus refers to the genetic material that acts intracellularly (the infectious particle).

Question 5

Explain the role of glycoproteins in the influenza virus cycle and how it leads to the continuing prevalence of the virus in the population.

Answer 5

Two key glycoprotein in influenza are called hemagglutinin and neuraminidase. Hemagglutinin binds with sialic acid on the surface of a host cell and initiates endocytosis, after which genetic material can be released. Neuraminidase enables the replicated virus to leave the host cell.

These glycoproteins act as identity markers for the virus. However, mutations in the genes coding for these proteins lead to different strains of influenza, by creating versions of H and N glycoproteins.

Question 6

Explain the method of viral replication in a host cell.

Answer 6

After the viral genome is taken up by the host by injection or endocytosis, translation of necessary protein and capsid synthesis occurs.

For viruses thats uses RNA as its genetic material, RNA acts as template for protein synthesis, or in the case of retrovirus, RNA will be converted to DNA using reverse transcriptase.

DNA viruses replicate replicate genome in nucleus and direct capsid synthesis via mRNA.

Question 7

What are prions? How does it work?

Answer 7

infectious particle of protein (no nucleic acid), it triggers a chain reaction in which normal prion protein is converted into an infectious prion