Introduction to Viruses

Question 1

What are viruses?

Answer 1

Acellular microorganisms (biological) that cannot survive without a host: no metabolic abilities of their own “a borrowed life”

Question 2

What do viruses rely on?

Answer 2

Completely on biosynthetic machinery of an infected cell to multiply

Question 3

What is the most abundant biological entity on earth?

Answer 3

Viruses

Question 4

What are viruses also?

Answer 4

Parasitic entities that hijack molecular resources of the host

Question 5

What size is viruses?

Answer 5

10-400nm

Question 6

What do viruses consist of?

Answer 6

2 parts and in some cases a third part

Question 7

What are the 2 parts of the virus?

Answer 7

genetic material and capsid

Question 8

What is the genetic material?

Answer 8

Made from either DNA or RNA

Question 9

What is a capsid?

Answer 9

A protein coat that surrounds and protects the genetic material

Question 10

What is the third part of a virus?

Answer 10

Envelope of lipids

Question 11

What does the envelope of lipids do?

Answer 11

Surrounds the protein coat when they are outside the cell

Question 12

What are capsids made of?

Answer 12

Multiple units of the same protein building block known as capsomers

Question 13

What are capsomers?

Answer 13

Subunit of the capsid arranged in a precise and highly repetitive pattern around the nucleic acid

Question 14

How many types of symmetry is there for capsids and capsomers?

Answer 14

3

Question 15

What are the 3 types of symmetry?

Answer 15

Helical, icosahedral and complex

Question 16

What is the helical arrangement?

Answer 16

Nucleic acid within helical structure of capsomers

Question 17

What is the size of helical?

Answer 17

18x250nm

Question 18

What is icosahedral?

Answer 18

20 face polyhedron- each face is an equilateral triangle-icosahedron

Question 19

What is the size of icosahedral?

Answer 19

70-90nm diameter

Question 20

What is complex?

Answer 20

The head has icosahedral symmetry and tail is helical

Question 21

What is the size of complex?

Answer 21

80x225nm

Question 22

What is the viral genome made up of?

Answer 22

Nucleic acid (DNA or RNA)

Question 23

What could the viral genome be?

Answer 23

linear, circular or segmented

Question 24

What can the sizes of the viral genome vary from?

Answer 24

4,000 to 1 million nucleotides (3 genes to 100-1000)

Question 25

What possible forms of RNA and DNA are found in viruses?

Answer 25

Single stranded and double stranded RNA and DNA

Question 26

What do viruses infect?

Answer 26

All cell types ad all forms of life

Question 27

What is the host organism?

Answer 27

An organism a virus infects

Question 28

What is the host cell?

Answer 28

A cell a virus multiplies in

Question 29

What are bacteriophages?

Answer 29

Viruses that infect and replicate in bacteria

Question 30

What were bacteriophages heralded as?

Answer 30

A potential treatment for diseases such as typhoid and cholers

Question 31

What are the types of bacteriophage infections in bacteria?

Answer 31

Lytic infection (virulent) and Lysogenic infection

Question 32

What happens in lytic infection?

Answer 32

Host cell dies

Question 33

What is the first step of lytic infection?

Answer 33

Attachment

Question 34

What happens after attachment?

Answer 34

Entry of phage DNA and degradation of host DNA

Question 35

What happens after entry of phage DNA and degradation of host DNA?

Answer 35

Synthesis of viral genomes and proteins

Question 36

What happens after synthesis of viral genomes and proteins?

Answer 36

Self assembly (complex and highly regulated)

Question 37

What happens after self assembly?

Answer 37

Release

Question 38

What is the burst size?

Answer 38

100-200 particles

Question 39

What is the length of the lytic cycle?

Answer 39

20-30 minutes

Question 40

What happens in lysogenic infection?

Answer 40

Host cell survives

Question 41

What is the first step of lysogenic infection?

Answer 41

Phage DNA integrates into bacterial chromosome >> prophage

Question 42

What happens after phage DNA integrates into bacterial chromosome?

Answer 42

Phage genome is silent- transcription of prophage genes is inhibited - does not kill the host

Question 43

What happens after phage genome is silent- transcription of prophage genes is inhibited - does not kill the host?

Answer 43

Prophage is copied with bacterial chromosome

Question 44

What happens after prophage is copied with bacterial chromosome?

Answer 44

Many cell divisions create many infected bacteria (daughter cell with prophage)

Question 45

What happens after many cell divisions create many infected bacteria (daughter cell with prophage)?

Answer 45

Occasionally, a prophage exits the bacterial chromosome initiating a lytic cycle

Question 46

What happens first in the HIV life cycle?

Answer 46

Entry and removal capsid proteins

Question 47

What happens after entry and removal of capsid proteins?

Answer 47

Synthesis of a DNA strand complementary to the viral RNA

Question 48

What happens after synthesis of a DNA strand complementary to the viral RNA?

Answer 48

Incorporation of double stranded DNA into the cells DNA

Question 49

What happens after incorporation of double stranded DNA into the cells DNA?

Answer 49

Transcription of proviral genes and manufacture of viral proteins

Question 50

What happens after transcription of proviral of double stranded DNA into the cells DNA?

Answer 50

Assembly of new virus particles

Question 51

What happens after assembly of new virus particles?

Answer 51

Exit of new virus particles from the cell