Lesson 7: Virus and Viral Genome

Question 1

An obligate intracellular parasite.

Answer 1

Virus

Question 2

True or False: We can culture a virus even though it is outside a host.

Answer 2

FALSE. A VIRUS is CANNOT BE CULTURED if it is outside its host since viruses lack metabolic machinery of their own and are totally dependent on their host cell for replication, they cannot be grown in synthetic culture media.

Question 3

True or False: The size of a virus is 0.02 to 0.3 μm.

Answer 3

FALSE. 0.02 to 0.3 μm is the SIZE OF A VIRION. The VIRUS is 20-500 nanometers in diameter.

Question 4

True or False: Viruses must live inside a host cell but not all of them cause disease.

Answer 4

TRUE

Question 5

True or False: Viruses can be found in all types of organisms.

Answer 5

TRUE

Question 6

True or False: We can see a virus using a light microscope.

Answer 6

FALSE. We CANNOT SEE A VIRUS because it is too small to be seen UNDER A LIGHT MICROSCOPE. The light microscope cannot show anything smaller than half the wavelength of visible light – and viruses are much smaller than this.

Question 7

True or False: The size of the virion is 20-300 nanometers.

Answer 7

TRUE. This is the conversion of 0.02-0.3 μm in nanometers. Take note of the conversion unit.

Question 8

What do you call a complete, fully developed, infectious viral particle?

Answer 8

Virion

Question 9

Name the 3 main structures and sub-structure of a virus. [Also called components]

Answer 9

1. Nucleic acid
2. Capsid
   Capsomere
3. Envelope

Question 10

It is either DNA or RNA.

Answer 10

Nucleic Acid

Question 10

A protein coat that surrounds the nucleic acid.

Answer 10

Capsid

Question 11

Each capsid is composed of these protein subunits.

Answer 11

Capsomere

Question 11

The one that covers the capsid.

Answer 11

Envelope

Question 12

Those that are not covered and are usually composed of combinations of lipid, protein, and carbohydrates. It may or may not be covered with spikes.

Answer 12

Non-enveloped or naked virus

Question 13

It is a unit of viral structure, consisting of a capsid with the enclosed nucleic acid.

Answer 13

Nucleocapsid

Question 14

Name the 4 Viral Shapes

Answer 14

1. Helical Viruses
2. Polyhedral Viruses
3. Enveloped Viruses
4. Complex Viruses

Question 15

Identify the viral shapes in the photo.

Answer 15

1. Complex (Bacteriophage)
2. Spherical (Influenza)
3. Polyhedral (Adenovirus)
4. Helical (tobacco mosaic virus)

Question 16

Long rods that may be rigid or flexible. The nucleic acid is found within a hollow, cylindrical capsid that has a helical structure.

Answer 16

Helical Viruses

Question 17

The shape of an animal, plant, and bacterial virus. Its capsid is in the shape of an icosahedron (20 triangular faces, and 12 corners). The capsomeres are equilateral triangles.

Answer 17

Polyhedral Viruses

Question 18

A roughly spherical shape.

Answer 18

Enveloped viruses

Question 19

Give the 2 types of enveloped viruses.

Answer 19

1. Enveloped Helical Virus: helical virus enclosed with an envelope.
2. Enveloped Polyhedral Virus: polyhedral virus enclosed with an envelope.

Question 20

Bacterial viruses which have a complicated structure.

Answer 20

Complex viruses

Question 21

What is the 3 viral symmetry?

Answer 21

1. Helical symmetry: rod shape viruses
2. Icosahedral: spherical shaped virus
3. Complex: composed of several separate capsomere with separate shape and symmetry

Question 22

It is consists of either DNA or RNA, single/double-stranded, and can either be linear or circular.

Answer 22

Viral genomes. [Genomes = complete genetic information (either DNA or, in some viruses, RNA) of an organism, typically expressed in the number of basepairs.]

Question 23

Explain the base sequence of a Viral Genome.

Answer 23

> Single-stranded genome + sense or = sense.
Plus configuration: have the exact same base sequence as that of the viral mRNA that will be translated to form viral proteins.
Minus configuration: complementary in base sequence to viral mRNA.

Question 24

What are the living characteristics of a viral genome?

Answer 24

1. Reproduce at a fantastic rate (only in living host cells).
2. Can mutate

Question 25

What are the non-living characteristics of a viral genome?

Answer 25

1. Acellular (contain no cytoplasm/cellular organelles)
2. Carry out no metabolism on their own and can only replicate using host cell’s metabolic machinery.
3. Either DNA or RNA.

Question 26

Name the 2 double-stranded DNA Bacteriophages.

Answer 26

1. Bacteriophage T7

2. Bacteriophage Mu

Question 27

Name the viruses with RNA Genome.

Answer 27

1. Positive Strand RNA Viruses.
   a. Bacteriophage MS2
2. Negative strand RNA Animal Viruses
3. Double-stranded RNA viruses
4. Viruses that Uses Reverse Transcriptase