Fuck my life <3333

What are viruses?

small particles that can replicate inside living cells

What kind of parasites are viruses?

obligate intracellular parasites

What can viruses infect?

All forms of life (including bacteria)

What did Walter Reed and his team discover?

yellow fever was a virus transmitted by mosquitos

How is yellow fever transmitted?

By mosquitos

In 1935, what did Stanley from Columbia University do?

Crystallized the tobacco mosaic virus

What did Stanley from Columbia University win?

a nobel peace prize

Virus is the latin word for what?

poison

What is an example of viruses plaguing humans before we knew what they were?

Smallpox in Egypt

What happened to the infectious tobacco mosaic virus?

It was isolated in a filtered, bacteria-free fluid

What is the typical size of a virus?

10-100 nanometers

What is the genome size range of a virus?

a few 1000 to 200,000 nucleotides in length

What do most viruses contain?

a single genetic molecule

What do few viruses contain?

segmented genomes

The genetic material of viruses can either be?

single or double stranded (DNA or RNA)

What is the host of the Poliovirus?

Humans

What is the host of the Tobacco mosaic

virus?

Tobacco and

related plants

What is the host of the T4?

Eschericia coli

What is the host of the Variola virus?

Humans

What is the host of the Mimivirus?

Amoeba

What is the structure of Poliovirus

Non-enveloped,

icosahedral

What is the structure of Tobacco mosaic

virus?

Non-enveloped,

helical

What is the structure of T4?

Non-enveloped

What is the structure of Variola virus?

Enveloped, complex

What is the structure of Mimivirus?

Enveloped, complex

What is the size of Poliovirus?

30

What is the size of Tobacco mosaic

virus?

300 × 18

What is the size of T4?

200 × 90

What is the size of Variola virus?

300 × 250

What is the size of Mimivirus?

400

What is the genome size of pollovirus?

7,700

What is the genome size of Tobacco mosaic

virus?

6,400

What is the genome size of T4?

170,000

What is the genome size of Variola virus?

186,000

What is the genome size of Mimivirus?

1,200,000

What is the genetic material of Poliovirus?

ssRNA

What is the genetic material of Tobacco mosaic

virus?

ssRNA

What is the genetic material of T4?

dsDNA

What is the genetic material of Variola virus?

dsDNA

What is the genetic material of Mimivirus?

dsDNA

Viral genome is surrounded by one or more viral proteins called?

capsid

Capsid of all viruses consists of many arranged subunits, also known as what?

capsomeres

Each capsomere is made up of one or more what?

poly peptide

What are the shapes that capsids often exhibit?

helical or icosahedral

Most shapes with helical capsid symmetry contains what?

single standard RNA genomes

What is an example of helical viruses?

ebola virus and TMV

What is an example of icosahedral viruses?

Rhinovirus (common cold), Adenovirus, and poliovirus

Viruses of bacteria typically exhibit what kind of characteristics?

icosahedral head and helical tail

What do the tail fibers of the virus help?

Helps binding to host cells

What is the name of the capsid and genome together?

nucleocapsid

The protein shell (capsid) around genome is composed of many what?

capsomere proteins

What is an enveloped virus?

When a plasma membrane surrounds the nucleocapsids

What is a naked virus?

when there is NO plasma membrane surrounding the capsid

What are examples of enveloped virus?

Influenza virus and HIV

What are “spikes”?

glycoproteins inserted into the lipid membrane

What determines the subtype of influenza

hemagglutinin and neuraminidase (spike proteins)

Most viruses with helical capsid symmetry contain what kind of genome?

ssRNA genomes

What 3 steps must a virus do in the replication cycle of viruses?

• A virus must stick to a host cell

• get into the host cell

• release into the genome

• (synthesis)

• (assembly and exit)

What is the most important part of the viral replication cycle?

Entry

What do the mechanisms for entry (of a virus) depend on?

the host cell

Do animal viruses have to contend with a cell wall structure?

No;

Animal viruses don’t have to contend

with a cell wall structure.

Do plant, fungal, and bacterial viruses have to contend with a cell wall structure?

Yes;

Plant, fungal, and bacterial viruses do

Entry of viruses often depends on what?

(some) damage to the plant tissues to open a spot in the cell wall

What are examples of damage to plant tissues?

• Insects feeding on plants

• Wind damage, Hail/rain damage

• Fire damage, Human-induced damage

In the case of bacteria, virus particles DO NOT do what?

enter the host cell after the attachment on the bacterial cell surface.

In the case of bacteria, what happens to the virus particles?

conformational changes occur in protein units of the tail of the virus

In the case of bacteria (in the replication cycle of viruses), where does DNA move?

DNA moves from the capsid head into the cytoplasm of the bacterial cell

In the case of animal cells, once a viral particle has attached to a host cell, what happens?

some form of a viron capsid or viral genome enters the cytoplasm of the cell.

For non enveloped animal viruses, the entire viral particle enters the cell through what?

endocytosis

Enveloped viruses like HIV undergoes what at the cell surface?

member fusion event

Enveloped viruses like influenza first enters the cell through what/

endocytosis

(Animal cells)

After entry, the viral capsid undergoes a specific set of disassembly or uncoating that results in what?

The release of the genome in the cytoplasm of the host cell

What are the three hypothesis of the origins of viruses?

• Coevolution

• Regressive

• Progressive

What does coevolution (the first hypothesis of the origin of viruses) state?

viruses co-evolved with their current cellular hosts or existed before cells

What can the coevolution hypothesis explain the origin of?

many RNA viruses, but there is little support to this evidence

What does regressive (the second hypothesis of the origin of viruses) state?

Viruses are cells that lost some of the replicative and metabolic traits over time and are dependent on host cells.

What can the regressive hypothesis explain the origin of?

viruses of nucleocytoplasmic large DNA viruses

What does the regressive hypothesis NOT explain the origin of?

RNA viruses

What does the progressive (the third hypothesis of the origin of viruses) state?

Existing genetic elements

gradually gained the ability to move from cell

to cell.

What can the progressive hypothesis explain the origin of?

retroviruses and the replication of retrotransposons

Where have retroviruses may have evolved from?

eukaryal retrotransposons

What is evidence for the progressive hypothesis (for DNA viruses)

transposons

What is evidence for the progressive hypothesis (for retroviruses)

retrotransposons

What is the first step of transposons moving in a genome?

converting DNA to RNA

What is the second step of transposons moving in a genome?

RNA is converted back into DNA by a reverse transcriptase enzyme

What does the reverse transcriptase enzyme do (in relation of transposons)?

transcribes mRNA into DNA;

What can the copy of DNA made by the reverse transcriptase enzyme do?

Be integrated at a different location on the chromosome

Besides retrotransposons, retroviruses also undergo what?

RNA to DNA conversion.

The genetic organization of retroviruses resembles what?

the genetic organization of retrotransposons.

When are host cells are inoculated with the virus and the resulting progeny viral particles are

harvested?

viral replication

Non-enveloped viruses enter animal cells through what?

endocytosis

enveloped viruses enter animal cells through either

the fusion of their membrane with the plasma membrane of the host cell or through

endocytosis followed by disassembly

To cultivate viruses, host cells must be what?

inoculated with the virus and then harvest the resulting progeny viruses

For the cultivation of bacteriophages, a culture of actively growing bacteria is inoculated with what?

a small sample of phage

As the phage replicates and lysis the bacterial cells, the growth medium changes from what to what?

turbid to clear

After incubation, the medium is centrifuged and the resulting supernatant, that contains the viral progeny, is what?

filtered to obtain a cell-free sample of phage

To isolate a viral clone, bacterial cells are mixed with what?

A phage sample

After the phage is attached to the cells, a molten nutrient agar is what?

Added to the cells and poured onto a plate

Viruses replicate and infect what?

neighboring cells.

The presence of agar inhibits what?

the free movement of viruses