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MMI Intro > Viruses, Cancer & Prions > Flashcards

Viruses, Cancer & Prions Flashcards

1
Q

What does Herpes Simplex 1 cause?

A

Typically cold soars, rarely gential warts

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2
Q

What does Herpes Simplex 2 cause?

A

Genital warts, rarely cold soars.

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3
Q

Do virus have RNA and DNA?

A

No they have one or the other

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4
Q

What is a virus?

A

A small particle consisting of nuclei acid enclosed in a protein coat (capsid) and sometimes a membranous envelope

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5
Q

What do viral genomes consist of?

A

Either double/single strand of DNA/RNA

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6
Q

What is a capsid?

A

A protein shell that encloses the viral genome.

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7
Q

What do some virus have but not all?

A

An envelope

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8
Q

What is an envelope?

A

Membranes are derived from host membrane and contain a combination of viral and host cell glycoproteins.

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9
Q

What is the purpose of a glycoproteins (sugar protein)

A

It can help them bind to infect host cells

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10
Q

Is a naked or enveloped virus more affected by disinfectants?

A

Enveloped

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11
Q

What are different virus structures?

A

Helical, polyhedral, enveloped, complex

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12
Q

What does it mean for a virus to be helical?

A

Hollow cylindrical (tobacco mosaic virus.)

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13
Q

What is a polyhedral structure?

A

Forms triangular wedges ie)polio virus

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14
Q

What is an enveloped structure?

A

Membrane acquired from host around the capsid. Ie) herpes, hiv

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15
Q

What is a complex structure?

A

Extra feature ie) lateral body.

Seen in small pox and bacterial phages

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16
Q

How are virus classified?

A

1) type of nucleic acid (dsDNA)
2) replication strategy (enters the nucleus)
3) morphology (enveloped icosahedral)
4) host
5) type of disease they cause

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17
Q

What is the ICTV system of classification for viruses?

A

Uses families, sub families end in -viridae
Genus names end in -virus
Species names are often English names

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18
Q

What is the Baltimore system of classification?

A

Based on type of nucleic acid (RNA), strandedness (single vs. Double) and method of replication

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19
Q

What is the use of the Baltimore system.

A

It helps understand the biology Nd replictive cycles of a huge numbe of viruses. (# = more info)

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20
Q

What do all viruses have to do?

A

Make RNA that can be read by host ribosome.

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21
Q

What is an example of a DNA virus and how do they replicate?

A

Ss and ds DNA virus replicate there genetic material similar to living cells ie) herpes

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22
Q

How do RNA virus replicate and give an example.

A

RNA virus use a virally -encoded RNA-dependent RNA polymerase to make copies of their genome and mRNA
->use strands directly as template.
DsRNA = rotavirus
+ssRNA->directly uses as mRNA = poliovirus
-ssRNA->must first transcribe RNA to positive sense mRNA = rabiesvirus, influenzavirus.

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23
Q

What is unique about retroviruses?

A

They have a unique enzyme call reverse transcriptase.

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24
Q

What does reverse transcriptase do?

A

Reverse transcribes its genome. Converts ssRNA->dsDNA

25
Q

How do retro viruses infect?

A

It coverts its ssRNA to dsDNA and gets incorporated into the hosts cell genome prior to expression of the viral genes.
Eg)HIV

26
Q

How do does DNA Reverse transcribing viruses work?

A

These viruses encode their DNA to a mRNA and an RNA replicative intermediate. The RNA is then reverse transcribed to DNA by a virally encoded reverse transcriptase.
Eg) Hepatitis B

27
Q

What is a protein tail?

A

Part of a phage-> the protein tail attaches the phage to the host and injects the phage DNA inside

28
Q

What is a lytic cycle?

A

= death of host cell.

Produces new viruses and digests the host’s cell wall releasing the progeny viruses.

29
Q

What are the 6 stages of the lytic cycle?

A

1) attachment ->tail fibres recognize surface molecules
2) Entry-> can have an enzyme to digest through cell wall and inject genome.
3) Viral gene expression
4) DNA & Protein synthesis: production of virus DNA and protein
5) Assembly/Maturation: assembly of phage particle
6) Release: peptioglycan digestive enzyme to release of phage

30
Q

What is a lysogenic cycle?

A

Replicates virus genome without destroying the host. The DNA is incorporated into the host’s chromosome. =called a prophage or provirus.
An environmental signal triggers the virus genome to exit and switches to lytic mode.

31
Q

Where do DNA viruses typically need to go?

A

To the nucleus

32
Q

How do glycoproteins on an envelope help a virus?

A

The glycoproteins can bind to specific receptors on molecules on the surface of a host. This allows the virus to enter via endocytosis when the plasma membrane and viral envelope fuse

33
Q

What is budding?

A

When viral envelopes are formed from the host cells plasma membrane.

34
Q

Where else are envelopes made?

A

At the Golgi apparatus

35
Q

What is direct penetration?

Give an example

A

Ie) polio

It binds to cell receptor and is blue to enter this way -> DNA in inserted into cytoplasm

36
Q

What is endocytosis? Give an example

A

Ie)Herpes

Binds to receptor on host cell. ->host cell thinks its food-> brought inside a vacuole

37
Q

What is membrane fusion. Give an example.

A

Ie) measles

Envelope fuses directly with host membrane

38
Q

Where do RNA viruses usually replicate?

A

Cytoplasm

39
Q

What do all viruses have to use of the hosts

A

Ribosomes

40
Q

What are the different exit strategies of a virus?

A

Lysis of cell, budding and exocytosis

41
Q

What are the pro and cons of lytic infections?

A

+ many copes
- causes cytoplasmic effects.
Ie) adenovirus, poliovirus

42
Q

Pro and cons of a chronic/persistent infection

A

+ virus is shed
+ doesn’t always harm the host.
- shed slowly
Ie) Hepatitis B

43
Q

Pros & cons of Latent infections

A

Virus is hiding in host DNA.
Triggered by external factors
Ie) herpes simplex 1

44
Q

What is an Oncogenic infection?

A

The virus mutates/transforms the host cell to cancer cells.

Ie) human papillmoavirus

45
Q

Explain what type of virus a papovaviridae is.

A

Papovaviridae (Papillomavirus):
Has dsDNA circular
naked, enters via direct penetration.
Symptoms: typically none, can cause warts of skin an mucosal cells (hands, feet, genitals).
Some can cause cervical cancers.
Pap test look for abnormal morphology of cervial cell.

46
Q

What is a tumour?

A

Mass of constantly dividing cells

47
Q

Describe Herpesvirus

A

Genetic: dsDNA (linear)
Entry: enveloped, induces endocytosis.
Can be latent.

48
Q

What are some different kinds of herpes virus?

A 
HHV-1 = herpes simplex virus 1 = cold sores
HHV-2 = herpes simplex virus 2 = gential warts 
HHV-3 = Varicella-zoster virus =chicken pox and shingles 
HHV-4 = Epstein-Barr virus= causes mono, can lose cause Burkitt’s lymphoma
49
Q

What belongs to Rhabdoviridae?

A

Rabies virus:

It’s a -ssRNA that enters via endocytosis. Infects the central nervous system of most mammals

50
Q

What is Zoonosis:

A

An infectious disease that can transmit to and from animals to humans.

51
Q

Describe Influenzavirus A,B, &C

A

Genetic: -ssRNA, several pieces H1N1
It’s enveloped and enters via endocytosis
Cause flus’

52
Q

What are the two proteins influenza uses for pathogenicity?

A 
Hemagluten = binds to cells (H1-H16)
Neuramindase = helps escape N1-N9
53
Q

What is antigenic shift?

A

When a cell is infected by two different kinds of virus everything gets re-assorted and it creates. Highly pathogenic strain

54
Q

What is a retrovirus?

A

HIV: +ssRNA (linear)
Has an envelope, uses membrane fusion
Has reverse transcriptase to copy its RNA genome into DNA. The DNA than gets incorporated via integrase (enzyme) into host DNA. (Called a provirus)
After a period of dormancy the cell transcribes DNA to RNA.
Cell translates RNA into protein. Maturation occurs as the capsid is reassembled. The virus is then released by budding (exocytosis)

55
Q

What is a prion

A

Proteincous infections particle

56
Q

Where to prions typically cause dmg?

A

typically in the brain of mammals.

57
Q

How do prions propagate?

A

By converting normal proteins into the prion version

58
Q

What are some examples of prion disease?

A

Scrapie in sheep, mad cow (bovine spongiform encephalopathy) and Creutzfeldt-Jakob disease

59
Q

Why are viruses not considered to be alive?

A

Because they are not capable of reproducing their own DNA. They require the host’s ribosome to duplicate

MMI Intro (7 decks)

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