2.2 Viruses

Question 1

Are viruses living organisms?

Answer 1

• No.

Question 2

Why are viruses not regarded as living organisms?

Answer 2

• They lack a metabolism of their own.

Question 3

What are 2 things that all viruses have?

Answer 3

• Core of nucleic acid.
• Surrounded by capsid - a protein coat.

Question 4

What is an additional features that some viruses have such as HIV have?

Answer 4

• Additional envelope of membrane made of lipids + proteins.

Question 5

How do antivirals work?

Answer 5

• Inhibiting viral replication by the host cells.

Question 6

When antivirals have not been developed, how is spread of viruses prevented?

Answer 6

• Disease control.

Question 7

What is an example of where disease control was used to reduce the spread of a virus?

Answer 7

• 2014 Ebola outbreak in West Africa.

Question 8

What are the systems of classifying viruses?

Answer 8

• Structure.
• Nucleic acid type.

Question 9

What is the λ (lambda) bacteriophage host?

Answer 9

• Bacterium.

Question 10

What is the structure of λ (lambda) bacteriophage?

Answer 10

• Head.
• Tail tube.
• Tail fibres.

Question 11

What is the size (nm) of λ (lambda) bacteriophage?

Answer 11

• Head dia 50-60.
• Tail length - 150.

Question 12

What is the nature of nucleic acid core in λ (lambda) bacteriophage?

Answer 12

• Double-stranded DNA.

Question 13

What is the copying of nucleic acid core in λ (lambda) bacteriophage?

Answer 13

• Double-stranded DNA transcribed to mRNA.

Question 14

What is the host of Tobacco Mosaic Virus?

Answer 14

• Plants, esp of tobacco fam.

Question 15

What is the structure of Tobacco Mosaic Virus?

Answer 15

• Capsid of polypeptide building blocks arranged in spiral around canal containing RNA.

Question 16

What is the size (nm) of Tobacco Mosaic Virus?

Answer 16

• Diameter - 18.
• Length - 300.

Question 17

What is the nature of the nucleic acid core in Tobacco Mosaic Virus?

Answer 17

• Single-stranded RNA.

Question 18

How is the nucleic acid core copied in Tobacco Mosaic Virus?

Answer 18

• RNA copied directly to mRNA.

Question 19

What is the host of Ebola virus?

Answer 19

• Human ( esp endothelial cells, liver cells, immune cells, etc.).

Question 20

What is the structure of Ebola Virus?

Answer 20

• “Snake” of RNA w outer protein coat.

Question 21

What is the size (nm) of Ebola Virus?

Answer 21

• Diameter - 80.
• Length - 130,000.

Question 22

What is the nature of nucleic acid core in Ebola Virus?

Answer 22

• Single-stranded RNA.

Question 23

How is the nucleic acid core copied in Ebola Virus?

Answer 23

• RNA copied directly to form mRNA.

Question 24

What does HIV stand for?

Answer 24

• Human Immunodeficiency Virus.

Question 25

What is the host of HIV?

Answer 25

- Humans (T helper lymphocytes).

Question 26

What is the structure of HIV?

Answer 26

- Enzymes + single-stranded RNA at centre. - 2 layers of protein coats. - Outside is capsule + glycoproteins.

Question 27

What is the size (nm)of HIV?

Answer 27

- Diameter - 120.

Question 28

What is the nature of the nucleic acid core in HIV?

Answer 28

- Single-stranded RNA.

Question 29

How is the nucleic acid core copied in HIV?

Answer 29

- RNA reverse transcribed into double-stranded DNA. - DNA incorporated into host cell’s DNA. - Later transcribed to form mRNA.

Question 30

What is the lifecycle of a λ (lambda) bacteriophage?

Answer 30

- Lytic cycle.

Question 31

What are the steps in the lytic cycle?

Answer 31

- Phage absorbed onto bacterium + injects it’s DNA. - Phage DNA replicated + bacterial DNA broken down. - Many new phage particles are made by bacterium. - Cell bursts + phage viruses are released. - Cycle repeats.

Question 32

What is viral latency?

Answer 32

- Period in which under control of specific latency genes, pathogenic virus remains dormant. - Virus or nucleic acid is present inside infected cell but does not control cell’s activities.

Question 33

What are the 2 types of viral latency?

Answer 33

- Episomal latency. - Proviral latency.

Question 34

What is episomal latency?

Answer 34

- Viral nucleic acid remains inactive but free in cytoplasm of nucleus of infected cell.

Question 35

What is proviral latency?

Answer 35

- Viral nucleic acid becomes incorporated into DNA of host cell. - Can become reactivated at any point.