Viruses compared with cells, and how viruses spread

Grade 9 Science Worksheet

Circle the best answer.

1. 1.

   Esme fills in step 3 of the copying cycle of a virus. What happens at the blank step?

   • The virus divides in two, and each half goes on to build its own proteins
   • The virus's own ribosomes read its genetic material and build its proteins
   • The host cell's machinery copies the genetic material and makes proteins
   • The finished virus particles pass out of the host cell into the surroundings

2. Read this first

   Use the table

   Phage Q attaches only where its tail fibers fit receptor R (model data)

   cell	type	receptor R on surface
   X	bacterium	yes
   Y	bacterium	no
   Z	plant cell	no

3. 2.

   Jun reads a table of cells. Phage Q attaches only where its tail fibers fit receptor R. Which cell or cells can phage Q infect?

   • Cell X, because it has receptor R for the tail fibers to fit
   • Cells X and Y, because both are bacteria and both have a plasma membrane
   • Cell Z, because a plant cell is larger than a bacterium
   • Cells X, Y and Z, because each cell has a plasma membrane

4. Phage card T (model data)

   stage	what the card records
   after entry	the phage DNA is copied many times inside the bacterium
   later	new phage particles are made inside the bacterium
   at the end	the bacterium bursts and the new particles are released

5. 3.

   Noah reads a model card for phage T. Which cycle does the card show?

   • Lytic cycle, because new particles are made and the cell bursts
   • Lysogenic cycle, because the bacterium keeps on dividing normally
   • Lysogenic cycle, because the phage DNA joins the host cell's DNA
   • Neither cycle, because a phage cannot copy itself in a bacterium
6. 4.

   Pia reads a model card for phage L. Which cycle does the card show?

   • Lysogenic cycle, because the bacterium bursts and releases the phage
   • Lytic cycle, because the phage has entered the bacterium
   • Lysogenic cycle, because the phage DNA is copied with the host DNA
   • Lytic cycle, because the phage DNA is copied

7. Prophage card (model data)

   time	what the card records
   before the stress	the phage DNA sits in the bacterium's own DNA as a prophage and is passed on at each division
   after the stress	some prophage DNA leaves the host DNA and new phage particles are made

8. 5.

   Tala reads a card about a prophage in bacteria after a change in conditions. Which cycle do the stressed bacteria begin?

   • No new cycle, because a prophage cannot leave the host DNA
   • Lysogenic cycle, because new particles are made
   • Lysogenic cycle, because the phage DNA stays in the host DNA
   • Lytic cycle, because the prophage leaves the host DNA

9. Model data

   particle	width
   model virion	100 nm
   model bacterium	2 µm

   1 µm = 1,000 nm.

10. 6.

    Zee compares a model bacterium with a model virion. How many times as wide as the virion is the bacterium?

    • 0.05
    • 2,000
    • 200
    • 20
11. 7.

    Ari imagines virions of this width lined up across one eukaryotic cell. How many virions fit across the cell?

    • 12,500
    • 20
    • 5
    • 200
12. 8.

    Bo uses the rule that a bacterium is about 100 times as wide as a virion. How wide is the model bacterium in µm?

    • 0.4
    • 4,000
    • 4
    • 0.04

13. Use this

    Route card (model). Flu viruses are carried in tiny droplets made when a person coughs, sneezes or talks. The droplets land in the mouth or nose of a person standing nearby.

14. 9.

    Kira reads a model route card. Which route does the card describe?

    • Touching a surface that carries the virus
    • Droplets made by a cough, a sneeze or talking
    • Vertical transmission, inherited from a parent
    • An insect that carries the virus to a new host

15. Use this

    Route card (model). A plant virus is carried by an insect. The insect pierces a leaf and makes a small tear in the leaf surface. Virus particles pass through the tear into leaf cells. A plant cell has a cell wall, and a plant virus has no way of its own to cross it.

16. 10.

    Ren reads about how a plant virus gets into a leaf cell. According to the card, why does the insect matter?

    • A plant cell has no wall, so the virus enters as an animal virus does
    • The insect makes the virus copy itself, since viruses need an animal host
    • The insect's saliva gives the virus a tail like a phage, so it crosses the wall
    • The tear lets the virus past the cell wall, which it cannot cross by itself