Microbiology Viruses L15

Question 1

Another name for viruses

Answer 1

Intracellular parasites

Question 2

Can viruses replicate outside living cells

Answer 2

No

Question 3

How do viruses replicate

Answer 3

Take advantage of host cell’s metabolic machinery to make copies of themselves

Question 4

Structure of Viruses

Answer 4

1) Nucleic acid (DNA Or RNA) - aka the genome

2) Protein coat (capsid)

Question 5

What is the genome and the capsid together referred to as

Answer 5

Nucleocapsid

Question 6

What is the capsid composed of

Answer 6

Repeating subunits called capsomeres. They are in a Icosohedral symmetrical pattern (20 equilateral triangular faces)

Question 7

Is the DNA or RNA in viruses single stranded or double stranded

Answer 7

It can be either

Question 8

What do retroviruses do

Answer 8

They have an enzyme (reverse transcriptase) which converts RNA into DNA

Question 9

Strategies that viruses use to infect and enter host cells

Answer 9

1) Attachment
2) Translocation
3) Genome insertion (naked virus) - only genome enters not the protein coat
4) Membrane fusion (enveloped virus) - only nucleocapsid enters not plasma membrane
5) Endocytosis and endosome formation after the cell takes in the virus

Question 10

Process of viral infectivity and replication

Answer 10

Virus enters cell and replicates, creating viral DNA at the same time viral DNA goes through transcription creating RNA, which goes onto to create capsid protein. The new viral DNA assembles inside the capsid proteins to create more virus (virions) particles

Question 11

Where does DNA replication occur

Answer 11

In the nucleus

Question 12

Where does RNA replication occur

Answer 12

In the cytoplasm

Question 13

How are corneal infections treated

Answer 13

Very carefully, as scarring will make the eye opaque and will not go transparent again. Immunosuppressive drugs are given to suppress immune system so the immune system doesn’t cause any unnecessary damage

Question 14

Routes of transmission for viruses

Answer 14

1) Respiratory droplets
2) Faecal-oral
3) Parenteral
4) Sexual activity

Question 15

Where can herpes simplex viruses remain latent

Answer 15

In sensory ganglia

Question 16

What are latent infections

Answer 16

Some viruses, a latent infection can be established after a primary infection (e.g shingles)

Question 17

How can you test for viruses

Answer 17

1) In vitro propagation in cultured cells
2) Serological tests screen for anti-viral antibodies
3) PCR and hybridisation techniques for molecular diagnosis

Question 18

Examples of anitviral agents and what are they called

Answer 18

They are called virucides, such as detergents and chloroform uv light

Question 19

What do antiviral agents target

Answer 19

Attachment, penetration, inhibition of replication in the viral life cycle

Question 20

How is passive immunity against viruses introduced

Answer 20

Using high doses of antiviral antibodies

Question 21

How is active immunity introduced

Answer 21

Immunisation with subunit or live attentuated virus

Question 22

What 3 species of chlamydia causes human disease

Answer 22

1) Chlamydia trachomatis causes urogenital infection, conjunctivitis and trachoma
2) Chlamydia pneumoniae causes sinusitis, bronchitis and pneumonia
3) Chlamydia psittaci can cause pneumonia

Question 23

How does chlamydia affect host cells and what does it prevent

Answer 23

By binding to receptors on host cells and are then endocytosed. It prevents cells from synthesising ATP