Chapter 2

Question 0

What makes a virus unique?

Answer 0

Viruses occupy a position between non living and living matter

Question 1

What is a virus?

Answer 1

A microscopic particle capable of reproducing only within living cells

Question 2

What is the size range for viruses?

Answer 2

20 to 400 nm. One nanometer is one billionth of a meter

Question 3

Name and explain two parts that make up most viruses

Answer 3

A virus consists of an inner nucleus acid core, or strand, surrounded by an outer protective protein coat called a capsid.

Question 4

There are 3 shapes of viruses: irregular, spherical, and rod-shaped. Give an example of each and what type of organism do they infect.

Answer 4

A rod shaped virus called the tobacco mosaic virus, infects the leaves of the tobacco plant.
A spherical shaped virus called the adenovirus infects animals.
A irregular virus called the bacteriophage infects bacteria.

Question 5

Referring to viruses, what is an envelope?

Answer 5

An extra protective coat of protein and fat

Question 6

5 examples of living characteristics of viruses:

Answer 6

1. Has nucleus acid core-RNA or DNA
2. Able to reproduce-in host cell only
3. Able to invade a host cell and take over it’s reproductive machinery
4. Causes a contagious disease
5. Able to mutate

Question 7

Non-living characteristics of Viruses:

Answer 7

1. No metabolic needs-doesn’t need to eat, sleep, breathe
2. Not made up of cells
3. Able to be crystallized-when liquid evaporates-can await a new host in this form-length of time varies

Question 8

Finish the sentence: because viruses have characteristics like living and non living things they are considered:

Answer 8

To be transitional between life and non-life

Question 9

Finish the sentence: viruses evolve and reproduce but they…

Answer 9

are obligate intercellular parasites

Question 10

What are the four main steps to viral reproduction?

Answer 10

1. Virus attaches to cell and nucleic acid enters cell-either injects RNA or DNA or whole virus enters cell
2. Replicate parts-nucleic acid, capsid, envelope…=synthesis
3. Assemble new virus from parts
4. Cell lysis or viral release from infected cell

Question 11

Viruses infect bacteria by which two cycles?

Answer 11

Lytic cycle and lysogenic cycle

Question 12

Explain the lyric cycle (viral reproduction)

Answer 12

Virus attacks cell, kills it and releases more viruses right away- follows 4 steps of viral reproduction. It caused the disease right away and is more virulent

Question 13

Define virulent

Answer 13

How quickly a virus reproduces and is spread. More virulent viruses tend to follow lytic cycle.

Question 14

Explain lysogenic cycle

Answer 14

Sometimes a virus doesn’t kill host cell right away or immediately cause disease-coexist with host. Virus stays dormant as a prophase in the cell for several generations. Viral DNA gets copied at each replication of host cell-passed on to offspring. Later, the virus is triggered or activated and causes the disease by entering the cell. A trigger may be time, stress, or other illness.

Question 15

What is a prophage?

Answer 15

Host DNA and virus DNA

Question 16

What is a retrovirus?

Answer 16

Has RNA as the genetic material. RNA is converted into DNA copy inside the host cell by an enzyme called reverse transcriptase. Follows the lysogenic pathway. Can mutate easily-hard to make vaccines for these ones. Infects mainly animal cells.
Examples: HIV, influenza

Question 17

What is a pathogen?

Answer 17

Disease-causing agents

Question 18

Name the system that defends the body against pathogens.

Answer 18

The immune system

Question 19

Explain the Non-Specific response and the specific response of the body

Answer 19

The immune system comprises two main components: non-specific defenses, which are the body’s first line of defense against disease, and specific defenses, which invoke a specific immune response once a particular pathogen gets past the body’s generalized defense.

Question 20

What is the body’s primary line of defense?

Answer 20

Skin, mucous, membranes, tears, digestive enzymes (Non-specific response)

Question 21

What is the body’s second line of defense?

Answer 21

Phagocytic white blood cells which engulf and destroy the pathogens like viruses, bacteria, etc…. (Non-specific response)

Question 22

What is the body’s tertiary line of defense?

Answer 22

Lymphocytes-white blood cells that produce antibodies (active immunity) specific response

Question 23

What are interferons?

Answer 23

When viruses succeed in invading an animal cell, small protein substances called interferons are produced. When released from virus-infected cells, they make it difficult for the virus to infect other cells. This occurs no matter what virus invades the body cells.

Question 24

What is an antigen?

Answer 24

A substance, usually protein in nature, that stimulates the formation of antibodies.

Question 25

What is an antibody?

Answer 25

Protein formed within the blood that reacts with antigens. They can flag pathogens for destruction and can change the virus shape so the virus can’t enter the cell.

Question 26

What is a host range?

Answer 26

The number of species a virus can infect.

Question 27

How many species does a narrow host range infect?

Answer 27

1-3 species. Example: human cold virus

Question 28

What is a broad host range?

Answer 28

Infects many different species. Example: rabies infects mammals and birds

Question 29

How does a virus identify the host cell?

Answer 29

By a “lock and key” system. Antigens on the outside of the virus fit into a specific receptor site on the host cells surface.

Question 30

What is a vaccine?

Answer 30

A weakened, diluted, or dead form of the virus that is infected (because saliva and stomach enzymes would destroy it) into the body to produce immunity. The body reacts to the shape of the virus and produces antibodies so immune system can fight off the disease. However, vaccines can also weaken your immune system as you can not fight off other diseases because your immune system is busy.

Question 31

What do vaccines prevent?

Answer 31

Outbreaks, infection, and death

Question 32

What are 4 harmful effects of viruses?

Answer 32

1. Causes disease, cancer
2. Causes brain damage (ex.measles)
3. Destroys organs (ex. Hepatitis-liver, heart)
4. Can be fatal

Question 33

What are 3 beneficial effects of viruses?

Answer 33

1. Vector for gene splicing (to replace the bad gene)
2. Biological control (control or eliminate other organisms)
3. Make vaccines

Question 34

How can you avoid viruses?

Answer 34

Vaccinations.
Good hygiene.
Abstinence.
Boil water where cleanliness is in question.
Eat healthy.

Question 35

Explain virus evolution.

Answer 35

Viruses were once just fragments of genetic material that came from cellular organisms (left over parts). This is why viruses are specific to certain cells (because they come from them).

Question 36

Explain the steps of the scientific method.

Answer 36

Observations
Question
Hypothesis
Experiment 
Analyze and interpret data
Hypyothesis supported
Further experimentation
Hypothesis continues to be supported
Report results (publish)

Question 37

What is the depth of field?

Answer 37

Distance in front or behind the specimen which appears to be in focus.

Question 38

How do you calculate the actual size of a specimen?

Answer 38

Number of times object crosses field

Question 39

How do you calculate the drawing size?

Answer 39

Drawing size (mm)
---------------------- 
Actual size (mm)

Question 40

What is the diameter of field?

Answer 40

How much of the slide you can see.

Question 41

What is the diameter of field on low power?

Answer 41

4mm or 4000 um

Question 42

What is the diameter of field on medium power?

Answer 42

2 mm or 2000 um

Question 43

What is the diameter of field on high power?

Answer 43

0.4 mm or 400 um

Question 44

What is the diameter of field with the oil lens?

Answer 44

0.2 mm or 200 um