viruses

Question 1

General information

Answer 1

• microscopic
• pathogenic
  consist of:
• genetic material (DNA/RNA)
• capsid (protein coating around genetic mat)
• envelope (has protein markers on it- not all have this)

Question 2

Virus reproduction (how + steps)

Answer 2

viruses invade a host cell and use the cells machinery to reproduce themselves

3 step of viral infection:
- attachment & penetration
- viral genome expression and replication
- assembly and release of new viruses

Question 3

1. Attachment & Penetration

Answer 3

viral attachment:
virus attaches to + enters the host cell

• the virus has specific “keys” to “unlock” specific types of cells
  (viruses are specific to their hosts)

Question 4

how are viruses specific to their host

Answer 4

1) protein on the viral envelope signal specific types of cells to let them in
2) protein match their hosts cells like a lock & key

Question 5

three ways the virus can enter the cell

Answer 5

a) punch a hole into the cell and inject their DNA
b) fuse their envelope with the cell membrane, allowing DNA inside
c) become phagocytosed (engulfed) by the host cell

Question 6

phagocytosis

Answer 6

when one cell engulfs another cell of virus whole

Question 7

bacteriophage

Answer 7

• also called “phage”
• a virus that infects bacteria

Question 8

name the two types of viral life cycles and characteristics

Answer 8

1) Lytic cycle: shorter-term illness
2) Lysogenic cycle: long-term, dormant viruses

Question 9

lytic cycle (simple explanation)

Answer 9

the host cell is used to replicate the virus and then the host cell is killed

Question 10

lytic cycle steps (5)

Answer 10

1) attachment: specific receptor proteins on viral envelope match virus to the host cell
2) penetration: viral genome is inserted into the host cell
3) biosynthesis: host cell machinery is used to copy, transcribe and translate viral genome, which encodes the building materials for new viruses and the viral assembly proteins
4) assembly: new viruses are put together
5) release: new viruses break open (kill=lyse) host cell, and new viruses are released to infect other cells

Question 11

lysogenic cycle (simple explanation)

Answer 11

viral genome is incorporated into the hosts genome

Question 12

lysogenic cycle steps (3)

Answer 12

1) virus attaches and genome enters host cell
2) viral DNA is inserted into hosts DNA
3) prophage is replicated when host cell replicates ( eventually prophage DNA leaves host DNA and enters lytic cycle)

Question 13

what is prophage

Answer 13

integrated genome

Question 14

dormant lysogenic infections

Answer 14

• during the lysogenic replication process, the virus appears dormant because the host does not get sick
• when the virus exits the lysogenic cycle, many cells are already infected therefore progression of the disease is much faster

Question 15

examples of lysogenic cycle human viral infections (4)

Answer 15

• Herpes simplex (herpes, cold sores)
• Varicella Zoster Virus (shingles)
• Human Papilloma Virus (Warts)
• Human Immunodeficiency Virus (HIV) (AIDS)

Question 16

timeline of lysogenic cycle viruses

Answer 16

host typically doesn’t show symptom for an extended period of time after being infected (could be months or years)

Question 17

examples of lytic cycle human viral infections (4)

Answer 17

• common cold
• influenza
• rabies
• tobacco mosaic virus

Question 18

timeline of lytic cycle viruses

Answer 18

host typically displays symptoms 3-14 days after being infected

Question 19

why are viruses non-living (6)

Answer 19

• don’t have their own energy metabolism
• don’t grow
• don’t reproduce on their own
• don’t waste products
• don’t respond to stimuli
• inactive until they invade a host cell

Question 20

positive uses for viruses

Answer 20

• have helped scientists understand new things about how DNA is used in the body
• used to manipulate DNA in model organisms
• control of harmful organisms in agriculture
• use as a capsule to deliver drugs to specific cells
• genetherapy
• virotherapy

Question 21

gene therapy

Answer 21

use viruses to insert a good gene into someone with a genetic defect or disorder

Question 22

explain the process of gene therapy

Answer 22

1) cells harvested from patient
2) in lab, virus altered so cannot reproduce
3) a gene is inserted into the virus
4) altered virus mixer with patients cells
5) cells become genetically altered
6) altered cells injected into patients body
7) altered cells produce desired protein

Question 23

gene therapy might cure…

Answer 23

• diabetes
• cystic fibrosis
• cancer
• hemophilia
• etc

Question 24

virotherapy (simple definition)

Answer 24

cancer prevention and control
- design a virus that will cause the death of cancer cells

Question 25

virotherapy methods (2)

Answer 25

1) triggering the immune system to attack the cancer cells 2) making a lytic virus that will specifically infect cancer cells- and cause lysis in those cells only

Question 26

oncolytic virus (definition)

Answer 26

a virus that specifically attacks and kills cancer cells

Question 27

challenges in virus-based therapy (3)

Answer 27

- pre-existing immunity to the viral vector - a strong immune response to the treatment could cause severe illness or death - if the virus inserts into another gene in the patient, could create new problems

Question 28

two similarities and differences between lytic and lysogenic cycle (theses are my own practice questions, answers may be wrong)

Answer 28

similarities: - both are mechanisms of viral reproduction - both reproduce thousands of copy’s of the original virus - both only occur within the host cell differences: - lytic short term vs lysogenic long term - lytic kills the host cell vs lysogenic doesn’t - lytic show symptoms fast after being infected vs lysogenic does not

Question 29

two similarities and differences between genetherapy and virotherapy (theses are my own practice questions, answers may be wrong)

Answer 29

similarities: - - differences: - -

Question 30

study the image