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Biology 260 > Unit 2 > Flashcards

Unit 2 Flashcards

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1
Q

What can viruses infect?

A

Animals, bacteria, and plants

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2
Q

Virus structure is composed of _________, __________, and/or __________ depending upon the type of virus.

A

Envelope, capsid, and genome (DNA or RNA)

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3
Q

Are viruses living?

A

No;

They need a host to infect

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4
Q

What are the stages of the Virulent phages Lytic Cycle?

A
  1. Attachment
  2. Entry
  3. Biosynthesis
  4. Assembly
  5. Maturation/Release (lysis)
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5
Q

In which stage is the viral DNA introduced into the cell in the Lytic Cycle?

A

Entry

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6
Q

In which stage of the Lytic Cycle does formation of mature viruses occur?

A

Assembly

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7
Q

The host DNA is usually degraded during which stage in the Lytic Cycle?

A

Biosynthesis

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8
Q

What would be the fate of a lytic bacteriophage if the host cell died prior to the assembly stage?

A

The virus would not be able to infect new hosts

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9
Q

What are the two types of life cycles that Temperate bacteriophages carry out?

A

The lytic cycle & the lysogenic cycle

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10
Q

What are the stages of the Temperate bacteriophages Lytic Cycle?

A
  1. Attachment
  2. Entry/Uncoating
  3. Biosynthesis
  4. Assembly
  5. Maturation/Release
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11
Q

What does the bacteriophages DNA form after penetration?

A

Lytic: circle

Lysogenic: circle; prophage

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12
Q

What are the two things the bacteriophages DNA can do after it becomes a circle?

A

Continue the lytic cycle or go on to the lysogenic cycle

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13
Q

What are the steps of the lysogenic cycle?

A
  1. Attachment
  2. Entry/Uncoating
  3. Synthesis
  4. Assembly
  5. Maturation/Release

(After Biosynthesis from lytic cycle)

  1. Recombination: the phage DNA integrates within the bacterial chromosome
  2. Induction: the prophage is excised from the host chromosome
  3. Re-enters the lytic cycle
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14
Q

Lysogenic viral DNA which has integrated into the host genome is referred to as?

A

A prophage

(When the bacterium reproduces the prophage is also copied)

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15
Q

How can induction occur in the lysogenic cycle?

A

Spontaneously through recombination, some other genetic event, through UV light, or certain chemicals

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16
Q

How is the lytic cycle different from the lysogenic cycle with respect to the infected host cell?

A

The host cell dies during the lytic stage

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17
Q

What is the fate of the prophage during the lysogenic stage?

A

It is copied every time the host DNA replicates

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18
Q

Contact between a phage and its bacterial host occurs by _____

A

A random collision;

As phages are incapable of movement

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19
Q

What portion of bacteriophage T4 enters E. coli?

A

Only the T4 genome enters the bacterial cell;

The capsid remains on the surface of the cell

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20
Q

Once entry/uncoating into the bacterial cell has been achieved, the next step in a lytic replication cycle is _____

A

Synthesis

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21
Q

During a lytic replication cycle, what action does a phage take to ensure that its host bacterium does NOT continue synthesizing cellular molecules?

A

Phage enzymes degrade the bacterial DNA

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22
Q

In a lytic cycle of replication, release of phages involves _____

A

The bacterial cell bursting open;

The bacterial cell undergoes lysis, meaning that it is destroyed. Phages are then released

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23
Q

A major difference between the lytic and lysogenic cycles of phage replication is that during the lysogenic phase _____

A

The phage genome inserts itself into the host genome (prophage)

24
Q

What factor may induce a prophage to enter the lytic cycle?

A

UV Light

25
Q

During the lysogenic cycle, it is possible for integrated phage genes to change the characteristics of the host cell. This is known as _____

A

Lysogenic Conversion;

Lysogenic conversion involves phenotypic changes to the bacterium due to new genes from the integration of the phage genome

26
Q

A basic stain has a ___ chromophore (stain-bearing ion)

A

Positively-Charged

27
Q

Which type of stain will bond to and color bacterial cells?

A

A basic stain

28
Q

The hanging-drop technique is very useful for observing a microbe’s __________

A

Motility

29
Q

The normal function of the PrP protein in mammals is believed to be:

A

Assisting in normal synaptic development and function

30
Q

How do normal prion proteins (PrP) differ from the infectious prion proteins?

A

Normal PrP have alpha-helices;

Infectious PrP have beta-pleated sheets

31
Q

How does the number of infectious prions increase?

A

Prions transform normal proteins into the misfolded beta-pleated sheet configuration; therefore, prions multiply by conversion

32
Q

Why are the beta-pleated multimers of PrP potentially pathogenic?

A

The multimers are more stable and resistant to protease

33
Q

What, in a wide number of species are associated with spongiform changes in brain tissue?

A

Prion diseases

34
Q

How can some prion diseases be transmitted?

A

Through the consumption of infected animal products (ex. contaminated beef or other animal products)

35
Q

Which test can confirm the presence of this prion disease?

A

Brain Scan;

The spongiform lesions noted on the brain scan are characteristic of prion diseases

36
Q

What is the typical incubation period for prion diseases?

A

Decades

37
Q

Which are the three mechanisms that animal viruses use to enter host cells?

A
  1. Endocytosis
  2. Membrane fusion
  3. Direct penetration
38
Q

What is Endocytosis?

A

When the virus is engulfed by the host cell into a vesicle, then the viral genome is released into the cell

39
Q

What is Membrane fusion?

A

When the viral envelope fuses with the host cell membrane, allowing the viral capsid and genome to enter the cell

40
Q

What is direct penetration?

A

When the viral capsid attaches to the host cell membrane, and the viral genome is injected directly into the cell

41
Q

What is the difference between membrane fusion and endocytosis?

A

In membrane fusion, the cell does not surround the virus with cell membrane

42
Q

A latent virus:

A

Can remain in the host for an extended time without causing any signs or symptoms;

Not all latent viruses insert into the host chromosome like prophage. If they DO, they cannot leave (unlike prophages)

43
Q

What is the first step to occur in HIV replication?

A

Reverse transcriptase makes DNA from a viral RNA template;

HIV has +ssRNA genome. Therefore, the RT uses it to make a complementary strand of viral DNA

44
Q

Which HIV enzyme is responsible for production of functional enzymes and capsomeres from a very large polypeptide?

A

Protease

45
Q

What is an example of a Latent viral infection?

A

Shingles caused by the herpes zoster virus

46
Q

(1) What is the correct sequence of events for the replication of a DNA virus?

A

Virions attach to the host cells

47
Q

(2) What is the correct sequence of events for the replication of a DNA virus?

A

Viral DNA is released into the nucleus of the host cell

48
Q

(3) What is the correct sequence of events for the replication of a DNA virus?

A

Enzymes required for multiplication of viral DNA are produced via transcription and translation and viral proteins are synthesized

49
Q

(4) What is the correct sequence of events for the replication of a DNA virus?

A

A copy of the DNA is made and the virions are assembled

50
Q

(5) What is the correct sequence of events for the replication of a DNA virus?

A

Capsid and other structural proteins are manufactured and virions mature

51
Q

(6) What is the correct sequence of events for the replication of a DNA virus?

A

Assembled virions are released from the host cell

52
Q

What disease does the human herpesvirus-1 cause?

A

Cold sores or fever blisters;

Painful, short-lived vesicles that form near the outer margins of the lips. Transmitted via oral and respiratory routes

53
Q

What happens to the Gram-positive cell wall during decolorization?

A

The decolorizing agent dehydrates the peptidoglycan but the color stays

54
Q

What happens to the Gram-negative cell wall during decolorization?

A

The decolorizing agent dissolves the outer membrane and removes the color

55
Q

As bacterial cells age, their peptidoglycan begins to break apart. What would be the effect on decolorization?

A

Old Gram-positive cells will be decolorized

56
Q

How does safranin affect Gram-positive cells?

A

Safranin penetrates the cell wall, but is masked by the darker crystal violet stain

Biology 260 (34 decks)

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