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Flashcards in Viruses Deck (24):
0

What genetic information do viruses contain?

-DNA or RNA not both
-No genes which encode for proteins used in protein synthesis, ie ribosomes
-May/May not encode for enzymes involved in nucleic acid synthesis

1

Describe the different structures of DNA/RNA found in viruses

-Linear, circular nicked
-ss or ds
-ss can be +sense or -sense
-segmented or unsegmented

2

What is meant by +sense RNA and -sense RNA?

-+sense can be used directly as mRNA
--sense has to be converted to +sense to be used

3

Why does segmented DNA/RNA have evolutionary significance?

-Two viruses infect the same cell
-reassortment of segmented DNA/RNA may produce a more virulent form

4

Can viruses live outside of cells?

-No they are obligate intracellular parasites

5

How are viruses usually diagnosed?

-Through molecular detection of genome, i.e. PCR
-Through the detection of specific immune responses

6

How are all viruses arranged? Describe this structure

-Into nucleocapsids
-Proteins arranged in a way which protects nucleic acid within from the harsh environment
-Helical or icosahedral
-Each individual subunit called capsomer

7

What is the major classification of viruses?

-Enveloped or naked

8

How are virus envelopes environmentally adapted?

-Contains lipids/glycoproteins which bind specific receptors on target cell membranes
-Glycoproteins mimic the host cell and the immune system cannot tell self from non-self

9

How are naked viruses protected from the human immune system?

-Virus infects cell
-Approaches pm and causes budding of the cell membrane in such a way that the virus becomes coated in cell membrane
-Cannot be recognised

10

What are the different viral classifications based on replication strategy?

-+RNAss -> directly translated
--RNSss -> converted to + to be translated as mRNA
--ssDNA -> has to be converted to dsDNA ->mRNA
-+ssDNA -> has to be converted to dsDNA->mRNA
-+dsRNA->has to be converted to dsRNA->mDNA

11

What is the inoculation period of viruses?

-asymptomatic replication stage of the virus which results in damage/dysfuction that is the symptom

12

How are viral infections described in terms of time?

-Acute, subacute, chronic, latent

13

What are the necessary requirements of a target cell for a virus?

-Must have appropriate cell surface receptors to initiate receptor mediated endocytosis
-Must have appropriate cellular machinery needed for replication
-After replication is successful, the cell must be permissive

14

What two other mechanisms, other than endocytosis, can viruses enter cells by?

-Coated pits
-Fusion with pm

15

What 4 effects can viruses have on cells?

-Cytopathic effects
-Cellular death
-Chromosomal damage
-Inhibition of cell protein synthesis

16

What are the cytopathic effects which viruses can have on cells?

-Inclusion bodies -> sites with active viral replication
-Syncytia formation-> giant multinucleate cells formed by fusion of pm

17

How are newly synthesised virus particles released?

-Bud from the cell
-Cellular lysis

18

What must be necessary for a virus to cause cancer?

-Integration of all or part of the virus genome into the host cell
-RNA reverse transcriptase to introduce/activate oncogenes
OR
-DNA viruses in non-permissive cells to deactivate tumour suppressor genes

19

What is the main cause of the resulting damage from infection?

-Inefficient host immune responses rather than microbe toxicity

20

Name a DNA enveloped virus

-Hepatitis B
-Small pox
-Herpesvirus

21

Name a naked DNA virus

-Papillomavirus

22

Name an RNA enveloped virus

-HIV
-Rubella
-Influenza

23

Name a naked RNA virus

-Polio