Name: _______________
Hr: ___
Viruses (19-2)
1. Label the picture below. Read the section “What is a Virus?” on page 478 to do this.
Head
DNA
Tail Fibers
Capsid
Surface
Proteins
Membrane
envelope
2. What is a virus made of? Core of DNA or RNA and a protein coat called a “capsid”;
surface proteins
3. What does the word virus mean? “poison”
4. Viruses that infect bacteria are called __bacteriophages___________.
5. Study the incorrect statements below. Change the underlined word(s) to make each
sentence correct. Write the correct new word(s) on the line.
a. Viruses are in the kingdom Archeabateria.
_not alive or not in a kingdom_
b. Viruses are made of cells.
_DNA/RNA and Capsid_
c. Viruses can be seen with a light microscope.
_an electron_
d. Viruses can cause damage only in humans.
_all kinds of organisms_
e. Each kind of virus infects several hosts.
_certain types of hosts_
f. Viruses are always larger than the cells
they infect.
g. Viruses reproduce outside of living cells.
__smaller___
__inside______
h. Viruses do not harm the cells in which they live. __kill_____
6. Using the section on lytic infection on page 480, put the following pictures in the correct
order. Also, describe what is happening at each stage.
4
Order
What is
happening?
1 virus attaches
itself to a
specific cell
1
2 virus
injects its
DNA/RNA
5
3 virus parts
are made
2
4 virus
parts are
assembled
3
5 cell gets so
full of viruses
it errupts
7. What is the difference between a lytic and lysogenic infection?
Lytic: virus enters cell, makes copies of itself, and causes cell to burst
Lysogenic: virus intergrates its DNA into the DNA of host cell, and viral genetic info
replicates along with the host cell’s DNA. Lysogenic infection can stay inactive for a
period of time and then enter the lytic stage (causing cell to burst)
8. Viruses are sometimes confusing to scientist because they show signs of acting both alive
and not alive. List three things they have in common with living things (cells).
a. Have a genetic code (DNA or RNA)
b. Change over time
c.
Reproduce (but require a host cell)
9. List three reasons why scientists do not believe viruses are alive.
a. no growth and development
b. don’t obtain and use energy
b. Don’t respond to environment
10. Read the section on Preventing Bacterial Disease, page 486.
Some bacterial and viral diseases can be prevented using a __vaccine____________.
What type of infection are antibiotics used for? _bacterial only, viruses will not respond to
antibiotics__________