module five: viruses

DISSCUSS 3 HYPOTHESES about how viruses evolved

1. virus-first hypothesis: viruses may be the precursors of life; predating or coevolving with their current cellular hosts.

2. regressive hypothesis: evolved from free living cells that became intracellular prokaryotic parasites

3. progressive hypothesis: originated from RNA and DNA molecules that escaped from a host cell and gained the ability to move

DESCRIBE the general structure of a virus

• nucleic acid core: contains the genome

• capsid: protective outer protein coat

• capsomere: proteins making up capsid

• envelope: coat that allows virus to attach and enter other cells

DESCRIBE the SIX steps of virus infection

• attachment: virus attaches to host

• entry: moves inside host

• uncoating: viral coating breaks down to release genetic material

• replication & gene expression: “hijacks” cellular machinery to transcribe viral genes

• egress: last stage, virion is released is able to infect adjacent cells and repeat replication cycle

IDENTITY some major viral illnesses that affect humans

• dna viruses: Herpes, Chicken pox, Human Papilloma Virus, Hep B

• rna viruses: SARS, measles, influenza, dengue

EXPLAIN why evolution is the key to understanding emergent diseases ("spillover" events)

spillover events is an evolutionary process that states that an infection in one host species can jump to a new host species

DISCUSS three types of therapy that involve using viruses to treat disease.

• body doesn’t make enough of something—virus delivers something to the host

• oncolytic viruses

• bacteriophages