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Intro To Biology: Evolution And The Diversity Of Life > Viruses And Prokaryotes > Flashcards

Viruses And Prokaryotes Flashcards

1
Q

Can viruses be classified as nonliving?

A

No, they can’t really be classified as nonliving either.

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2
Q

What is the cellular structure of viruses?

A

Viruses are non-cellular.

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3
Q

Do viruses have the ability to metabolize and grow?

A

No, they lack the ability to metabolize and grow.

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4
Q

Can viruses respond to external stimuli?

A

It’s unknown whether viruses can respond to external stimuli.

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5
Q

What do viruses possess that allows for adaptation and evolution?

A

Viruses possess a heritable genetic code.

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6
Q

What are viruses dependent on for reproduction?

A

Viruses are completely dependent on their hosts for reproduction.

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7
Q

What do viruses infect?

A

Viruses infect all domains of living organisms.

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8
Q

How do viruses vary?

A

Viruses vary widely in structure and means of replication.

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9
Q

What is an individual viral particle called?

A

An individual viral particle is called a virion.

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10
Q

What is the regressive hypothesis?

A

The regressive hypothesis states that viruses were once free-living cells or intracellular parasites that decreased in complexity and lost the ability to reproduce on their own.

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11
Q

What is another name for the regressive hypothesis?

A

The regressive hypothesis is also called the de-evolution hypothesis.

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12
Q

What is the progressive hypothesis?

A

The progressive hypothesis suggests that viruses arose from RNA or DNA, or from self-replicating mobile genetic material like transposons, that acquired the ability to leave their native host cell.

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13
Q

What is another name for the progressive hypothesis?

A

The progressive hypothesis is also called the escapist hypothesis.

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14
Q

What is the virus-first hypothesis?

A

The virus-first hypothesis suggests that viruses existed as the first self-replicating entities, predating cells.

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15
Q

How do viruses evolve?

A

Viruses adapt to their changing environments and evolve through natural selection, similar to living species.

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16
Q
A
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17
Q

What classification system is used to group viruses?

A

Viruses are grouped using the Baltimore classification system.

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18
Q

Who developed the Baltimore classification system?

A

The Baltimore classification system was developed by David Baltimore.

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19
Q

What is the main requirement for all viruses according to the Baltimore classification?

A

All viruses need to produce positive-strand mRNA from the genome to produce the proteins they require.

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20
Q

What factors are viruses grouped by in the Baltimore classification system?

A

Viruses are grouped based on their genomic structure, sense, and method of mRNA production during replication.

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21
Q

What types of genomes can viruses have?

A

Virus genomes can be made of RNA or DNA, and can be single-stranded (ss) or double-stranded (ds).

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22
Q

What is the genome of single-stranded RNA viruses referred to as?

A

The genome of single-stranded RNA (ssRNA) viruses is referred to as positive sense if it acts as mRNA for protein translation.

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23
Q

What is the abbreviation for single-stranded RNA?

A

Single-stranded RNA is abbreviated as (+)ssRNA.

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24
Q

What is the genetic sequence of negative-sense ssRNA viruses?

A

Negative-sense ssRNA viruses have a genetic sequence complementary to their mRNA.

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25
What enzyme do some viruses have that converts RNA to DNA?
Some viruses have an enzyme called reverse transcriptase, abbreviated RT.
26
What is the role of reverse transcriptase in retroviruses?
In retroviruses, reverse transcriptase converts RNA to DNA, which can then be incorporated into the host genome.
27
What are viruses?
Viruses are noncellular entities made of nucleic acids packaged in a protective capsid.
28
What is a capsid?
A capsid is a shell made of protein subunits, called capsomeres.
29
Do all viruses have an outer envelope?
Some viruses have an outer envelope, composed of phospholipids and associated proteins, acquired from their host cell.
30
What may a capsid contain besides the viral genome?
A capsid may contain proteins or enzymes in addition to the viral genome.
31
What are helical capsids?
Helical capsids are shaped like long cylinders.
32
What do icosahedral capsids look like?
Icosahedral capsids look like multifaceted three-dimensional spheres but are formed from 20 equilateral triangles.
33
What are enveloped viruses?
Enveloped viruses can have an icosahedral or helical capsid and possess a plasma membrane that's derived from their host surrounding their capsid.
34
What are complex viruses?
Complex viruses can have icosahedral and helical shapes with an outer cell wall or have the two shapes put together to form a head and tail.
35
What are the two main cycles for virus reproduction?
The two main cycles are the lytic cycle and the lysogenic cycle.
36
What happens in the lytic cycle?
In the lytic cycle, viruses quickly reproduce inside the host cell until it bursts open, releasing many new viruses.
37
What characterizes the lysogenic cycle?
The lysogenic cycle is slower and only seen in viruses that infect bacteria.
38
What occurs to viral DNA in the lysogenic cycle?
In the lysogenic cycle, viral DNA becomes a part of the host's genome and can persist for a long time.
39
What triggers the switch from the lysogenic cycle to the lytic cycle?
Environmental triggers cause the virus to switch to the lytic cycle.
40
Who first observed bacteria and in what year?
Antonie van Leeuwenhoek first observed bacteria in 1676.
41
What theory did Louis Pasteur support?
Louis Pasteur was an early supporter of the germ theory of disease.
42
What does the germ theory of disease state?
The germ theory of disease states that infectious microorganisms are pathogens responsible for causing illness.
43
What did Pasteur demonstrate through his experiments?
Pasteur demonstrated that microorganisms were responsible for fermentation and that living organisms didn't arise through spontaneous generation.
44
What did Pasteur conclude about spontaneous generation?
Pasteur concluded that his work disproved the theory of spontaneous generation.
45
What did Pasteur say about the origin of microscopic beings?
Pasteur wrote that there was no way that 'microscopic beings came into the world without germs, without parents similar to themselves.'
46
Who is Robert Koch?
A German physician and an early supporter of the germ theory of disease.
47
What are Koch's postulates?
A set of principles devised by Robert Koch to link a specific microorganism to a disease.
48
What is the first principle of Koch's postulates?
The microorganism can be found in high abundance in symptomatic individuals, and isn't present in healthy individuals.
49
What is the second principle of Koch's postulates?
The microorganism can be isolated from a symptomatic individual and grown in a laboratory culture.
50
What is the third principle of Koch's postulates?
Inoculating a healthy individual with the cultured microorganism produces the disease.
51
What is the fourth principle of Koch's postulates?
The microorganism in the inoculated, diseased individual can be retrieved and identified as the same microorganism from the original diseased host.
52
What are some limitations of Koch's postulates?
1. Seemingly healthy individuals can be asymptomatic carriers. 2. Pathogens like viruses and prions can’t be cultured. 3. Complex disease associations can’t be linked by a simple set of methodological principles.
53
What is horizontal transmission?
Horizontal transmission is the spread of an infection from one person to another, usually due to contact with bodily fluids.
54
What is vertical transmission?
Vertical transmission is the transmission of disease-causing microbes from a parent to offspring.
55
What are the two types of diseases based on duration?
Diseases can be classified as acute or chronic.
56
How do symptoms of acute diseases differ from chronic diseases?
Symptoms of an acute disease develop and resolve within a relatively short period of time, while chronic diseases last for longer periods of time or even indefinitely.
57
What is an outbreak?
An outbreak occurs when diseases occur suddenly and in high numbers within an area.
58
What is an epidemic?
An epidemic ensues when a disease outbreak spreads to a greater number of people over a larger area.
59
What is a pandemic?
A pandemic is declared if the original outbreak rapidly spreads to afflict multiple countries, continents, or the entire globe.
60
Can viruses infect all living organisms?
Yes, viruses can infect every living organism on the planet, but a single virus can only attack a limited range of cell types within one or a few species.
61
What is the most common oncogenic virus in cats?
The most common oncogenic virus in cats is the feline leukemia virus.
62
What are prions and viroids?
Prions and viroids are pathogenic subviral particles, smaller and simpler than viruses, capable of causing disease.
63
What is a prion?
A prion is a single viral protein that contains no genetic code.
64
What is a viroid?
A viroid is a circular strand of RNA.
65
What are prions known for?
Prions are proteinaceous infectious particles that cause diseases without containing genetic material.
66
What is the best-known example of a prion disease?
The best-known example of a prion disease is spongiform encephalopathy, commonly known as 'mad cow disease' or bovine spongiform encephalopathy (BSE).
67
How are prion diseases spread?
Prion diseases are spread by eating the nervous tissue of an infected individual.
68
What is kuru?
Kuru is a prion disease that affects humans, associated with cannibalism.
69
How can humans develop Creutzfeldt-Jakob disease?
Humans can develop Creutzfeldt-Jakob disease by eating beef infected with BSE.
70
How do prions behave in the intestinal tract?
Prions are extremely hardy and don’t break down in the intestinal tract.
71
What are the prions that cause disease?
The prions that cause these diseases are irregular variants of a normal protein produced by the host.
72
What are viroids?
Viroids are small, circular sRNA particles that aren't housed in a capsid nor do they produce any proteins.
73
What is the sole function of a viroid?
The sole function of a viroid is to reproduce its RNA sequence using the host cellular machinery.
74
What types of crops are affected by viroid diseases?
Viroid diseases affect agricultural crops, including potatoes, tomatoes, and avocados.
75
What is the economic impact of viroid diseases?
Viroid diseases cause significant losses costing millions of dollars every year.
76
What is Hepatitis D's relationship with viroids?
Hepatitis D has some properties like a viroid because it can only replicate in the presence of the hepatitis B virus.

Intro To Biology: Evolution And The Diversity Of Life (4 decks)

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