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Flashcards in viruses Deck (13)
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1
Q

Viruses differ from living cells in 3 major ways. What are they?

A
  1. they are acellular
  2. they have DNA or RNA- but not both
  3. they are unable to reproduce independently of cells
2
Q

Viruses lack the _______ needed for energy production and protein synthesis.

A

enzymes

3
Q

For viral production to occur, viruses must invade the ____ cell and cause the host cell to produce ____ and _____, which are later assembled to form the complete virus.

A

For viral production to occur, viruses must invade the HOST CELL and cause the host cell to produce VIRAL ENZYMES and VIRAL COMPONENTS, which are later assembled to form the complete virus.

4
Q

___________- exist for most, if not all bacteria

A

BACTERIOPHAGES ( phages, bacteria viruses, bacterial virions)

5
Q

Morphology of bacteriophages: _______ surrounded by a ____ composed of subunits called ______. The two most common symmetries are ______ and _______. The two major types of bacteriophages are _____ and ________ .

A

Morphology of bacteriophages: NUCLEIC ACID CORE surrounded by a CAPSID composed of subunits called CAPSOMERES. The two most common symmetries are ICOSAHEDRAL and HELICAL. The two major types of bacteriophages are LYTIC (VIRULENT) and LYSOGENIC(TEMPERATE OR AVIRULENT) .

6
Q

Viruses are cultivated in ________- in broth or on _____.

A

Viruses are cultivated in LIVING HOST CELLS(BACTERIA) in broth or on AGAR PLATES.

7
Q

_____________- may be used in phage typing for ____ of and identification of _______- bacteria. Bacteria are characterized by their resistance or susceptibility to a particular virus.

A

VIRULENT BACTERIOPHAGES may be used in phage typing for DETECTION of and identification of PATHOGENIC bacteria. Bacteria are characterized by their resistance or susceptibility to a particular virus.

8
Q

The _______- cycle: the multiplication process of a _____ bacteriophage is called a _____ cycle because the host bacterium is usually _____ in the final step of the _____- infection.

A

The LYTIC cycle: the multiplication process of a VIRULENT bacteriophage is called a LYTIC cycle because the host bacterium is usually LYSED in the final step of the VIRAL infection.

9
Q

What are the stages of the Lytic cycle? Explain them.

A
  1. adsorption: attachment of a particular virus to the cell wall of a specific bacterium. The attachment is at the specific receptor site for the virus.
  2. penetration: the injection of nucleic acid of the virus into the host cell (bacterium). Penetration may be chemical (lysozyme) and/or mechanical
  3. biosynthesis: nonessential host metabolism is shut down and the host genome is degraded. The host cell (bacterium) uses viral DNA to produce early proteins (enzymes) that degrade the host’s genome and replicate the viral DNA; the host then produces late proteins (enzymes) to synthesize viral components and to assemble those components during maturation
  4. maturation: viral DNA and capsids are assembled into complete viruses
    Eclipse: the period of time when no complete viruses are present
  5. lysis: phage lysozyme lyses bacterial cell wall and the replicated viruses are released. The number of viruses released per host cell is called the burst size.
10
Q

What is the lysogenic cycle?

A

The lysogenic cycle : viral DNA of temperate/avirulent phages is incorporated into host cell DNA as a prophage; the cell is not lysed and the viral DNA becomes a part of the bacterium’s chromosome. No RNA bacteriophages have been found to be temperate.

11
Q

What are the stages of the lysogenic cycle?

A
  1. Adsorption: attachment of a particular virus to the cell wall of a specific bacterium. The attachment is at the specific receptor site for the virus.
  2. Penetration: the injection of nucleic acid of the virus into the host cell (bacterium). Penetration may be chemical (lysozyme) and/or mechanical
  3. Lysogeny: insertion of viral DNA into the chromosome of the host (bacterium).
12
Q

What is lysogenic conversion?

A

An induced change in the phenotype of a host that is not directly related to completion of the life cycle of a virus.

13
Q

Animal/Plant viruses:
Structural composition .. _________ surrounded by a capsid (composed of subunits called ______ ). True ____ of the capsid; some viruses (virions) are enveloped viruses since they are enclosed by an outer ______ acquired form their previous host.

A

NUCLIEC ACID CORE surrounded by a capsid (composed of subunits called CAPSOMERES). True SYMMETRY of the capsid; some viruses (virions) are enveloped viruses since they are enclosed by an outer MEMBRANE acquired form their previous host.