Viruses

Question 1

what is a virus?

Answer 1

an infectious nucleic acid surrounded by protein

Question 2

describe viruses? 5 things

Answer 2

they are acellular
they are smalled than bacteria
they are derived from cells of other organisms
they have DNA and RNA
they replicate, mutate and evolve independently.

Question 3

what is viral phylogeny?

Answer 3

the analysis used for viral research

Question 4

why is viral phylogeny difficult to resolve?

Answer 4

the viral genomes are tiny which restricts the analysis that can be done.
also there are no known viral fossils.

Question 4

what is a virion?

Answer 4

a complete viral particle.

Question 5

describe the structure of a virion:

Answer 5

consists of a nucleocapsid (which is composed of nucleic acid) and a protein coat called a capsid.

Question 6

what does a capsid (protein coat) do?

Answer 6

the capsid surrounds the viral nucleic acid, protects the viral genome and helps in the transfer between host cells

Question 7

where can viruses be found?

Answer 7

they can exit intracellularly or extracellularly.
extracellular - where the viruses are inactive
intracellular - viruses exit as a nucleic acid

Question 8

viruses that affect bacteria are called?

Answer 8

bacteriophages (phages)

Question 9

how can viruses be classified?

Answer 9

based on the capsid

Question 10

what are the three types of capsid symmetry?

Answer 10

helical
icosahedral
complex

Question 11

helical capsid:

Answer 11

shaped like a hollow tube with protein walls
e.g tobacco mosaic virus
infects a wide variety of plants, especially tobacco

Question 12

icosahedral capsid:

Answer 12

a regular polyhedron with 20 equilateral triangular faces and 12 vertical.
e.g. chlorotic mottle virus

Question 13

complex capsid:

Answer 13

a combination of helical and icosahedral shapes

Question 14

what is poxvirus family?

Answer 14

the largest of animal viruses

Question 15

give an example of binal symmetry

Answer 15

T2, T4 and T6 have a final symmetry because they have a head that resembles an icosahedral and a tail that is helical

Question 16

what is a negative sense RNA virus?

Answer 16

they are a group of related viruses that have a negative sense, single-stranded genomes made of ribonucleic acid.

they use genome sense strands as the template for synthesis of all mRNAs.

Question 17

what is a positive sense strand RNA virus?

Answer 17

single-stranded RNA virus
replication is not needed before protein translation can take place.
includes most of the viruses that cause crop diseases. they cause patches of dead cells that look like a mosaic.

Question 18

what are retroviruses?

Answer 18

they are produced by reverse transcription.
it inserts a DNA copy of its RNA genome into the DNA of a host cell that it invades, changing the genome of that cell.

Question 19

what are double-stranded RNA viruses?

Answer 19

viruses may have evolved repeatedly from single-stranded RNA ancestors.

Question 20

What are double-stranded DNA viruses?

Answer 20

many common phages (bacteriophages) have double-stranded DNA viruses.

Question 21

describe a viral infection.

Answer 21

most viruses have protein on their surface membrane that binds to receptors on the host cell.
the protein tricks the cell into taking the virus
once, inside the organism, and the viral genes are eventually expressed.

Question 21

describe a viral infection.

Answer 21

most viruses have protein on their surface membrane that binds to receptors on the host cell.
the protein tricks the cell into taking the virus
once, inside the organism, and the viral genes are eventually expressed.

Question 21

describe a viral infection.

Answer 21

most viruses have protein on their surface membrane that binds to receptors on the host cell.
the protein tricks the cell into taking the virus
once, inside the organism, and the viral genes are eventually expressed.

Question 21

describe a viral infection.

Answer 21

most viruses have protein on their surface membrane that binds to receptors on the host cell.
the protein tricks the cell into taking the virus
once, inside the organism, and the viral genes are eventually expressed.

Question 22

what happens after a virus infects a cell?

Answer 22

inside living cells, viruses use their genetic information to make multiple copies of themselves.

Question 23

describe the 5 steps for viral life cycle.

Answer 23

1) attachment - also known as absorption, when the virus attaches to the host cell wall

2) penetration - when the nucleic acid or genetic info of the virus moves through the cell membrane into the host cell

3) replication- also known as biosynthesis, once inside the host cell, the virus forces the host cell to make components it needs for its replication.

4) assembly - AKA mutaration, when newly produces virus components are assembled into new viruses

5) release - when the completed viruses are released from the cell. they can now infect other cells and repeat the whole process again.

Question 24

what are papillomaviruses?

Answer 24

they are small DNA viruses associated with benign and lesions as well as cervical carcinomas.

Question 25

describe the structure of covid 19.

Answer 25

the virus has a spherical structure.
it has a diameter of 60 -140nm and with spikes of about 9-12nm.
the virus binds to ACE2 receptors which are present in the respiratory tract.