Viruses

Question 1

what are viruses

Answer 1

Simple nucleic acids (genomes) surrounded by a protein coat (capsid)

• do not metabolize or replicated independently
• can only reproduce with a host (obligate intracellular parasite)

Question 2

Host Range: What is the lock and key fit

Answer 2

viral surface links to host cell receptor molecule of same shape

Question 3

Explain the steps of the lytic cycle

Answer 3

1. Virus enters host cell
2. Genome is inserted, takes over host and replicates
3. New viruses formed
4. Lysis occurs - cell explodes and releases viruses

Question 4

Explain the steps of the lysogenic cycle

Answer 4

1. Virus enters host
2. Genome is inserted and incorporated into host cell’s genes (forms prophage/provirus)
3. Genome replicates alongside host
4. Virus leaves via environmental signal
5. Virus undergoes lytic cycle

Question 5

What is a prophage and why are they so dangerous?

Answer 5

They are viral genes incorporated in a host cell’s genes and go undetected

Question 6

Why cant antibiotics affect viruses

Answer 6

different structure and replication than bacteria

Question 7

How do viruses emerge (3)

Answer 7

mutation of existing viruses
spread from isolated sources
animal to human transmission/evolution

Question 8

What is a temperate phage and what is a virulent phage?

Answer 8

temperate: dormant bacteriophage which is integrated
virulent: active and dangerous virus that replicates

Question 9

What is a retrovirus

Answer 9

animal virus
reverses info flow from RNA to DNa
hard to detect
reoccuring infection
has reverse transcriptase (enzyme)

Question 10

what is a prion

Answer 10

affects plants (spread from soil to plants, can spread to animals/humans)
infectious misfolded protein
smaller than virus
no nucleic acid
cannot be destroyed
shrinks brain tissue

Question 11

what is a viroid

Answer 11

single stranded circular RNA
extremely small
no capsid
do not code for proteins, interferes with transcription
causes underdevelopment in plants

Question 12

Origin of viruses

Answer 12

Regressive: sourced from healthy cells
Progressive: sourced from escaped DNA/RNA
Coevolution: evolved alongside host cells

Question 13

Describe horizontal and vertical transmission

Answer 13

Horizontal: external source, spread via same generation of species
Vertical: internal source (inherited), spread from parent to offspring