Download Building viruses

Key Stage 3 | Lesson plan 2 - the wonderful world of germs Resource Sheet 2.2
Building viruses
Viruses are not living cells but they do share some of the characteristics
of living organisms.
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They can, for example, reproduce. However, a virus has no nucleus, no cytoplasm and no
surrounding membrane. Viruses cannot live freely, they can only survive in living organisms.
Viruses are much smaller than bacteria and can only be seen with an electron microscope.
Different types of virus have different shapes.
• The HIV virus is spherical.
• The tobacco mosaic virus which infects tobacco plants is rod shaped.
• Viruses called bacteriophages, which attack bacteria, have a more complex structure.
© Sebastian Kaulitzki
© 1994 Rothamsted Research
© Chris Dascher
The structure of a bacteriophage is shown in diagram 1 below and its life cycle is shown in
diagram 2. The bacteriophage uses its tail to attach itself to a bacterium (a) and then injects its
own DNA into the bacterium (b). This DNA contains all the information necessary to make the
bacterial cell’s ‘machinery’ start producing new bacteriophages (c and d). When the process is
complete, the new bacteriophages burst out of the bacterial cell to go and infect more bacteria (e).
}
Genome
(DNA or RNA)
Protein coat
}
Tail fibers
(a)
Icosahedral head
(b)
Tail
3D
(c)
2D
Base
plates
(d)
Diagram 1: The structure of a bacteriophage
(e)
Viruses are said to be infectious or pathogenic because
they are usually harmful to their host organisms.
Examples of viral diseases are influenza, the common cold
and rubella (German measles).
Diagram 2: The Life Cycle
of a bacteriophage
Photocopy the templates on the next pages onto card
and then cut them out to build your own viruses.
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Key Stage 3 | Lesson plan 2 - the wonderful world of germs Resource Sheet 2.2
Build Your Own Papovavirus
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Cut out the template to the
left and fold it so that it looks
like the shape above. This
is an icosahedron. It is also
the shape of the papovavirus
which infects humans and
causes warts. The outer case
of the virus is made of protein
and the DNA is held inside.
If you want to add a bit more
detail to your papovavirus
you could leave out one of
the triangular panels and put
a piece of string inside to
represent the DNA.
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Key Stage 3 | Lesson plan 2 - the wonderful world of germs Resource Sheet 2.2
Build Your Own Bacteriophage
Base plate
Cut out the template carefully above and glue it
together. This forms the ‘head’ of the bacteriophage.
Then either use a 10 cm length of drinking straw or a similar
length tube of paper to form the ‘tail’ of the bacteriophage.
Fix this to the head either by using sticky tape or by making
a small hole in the bottom of the head and poking the straw
through.
Cut out the circular base below and use sticky tape to fix this
to the bottom of the tail. Then fix six 10 cm lengths of pipe
cleaner to the base to form the bacteriophage’s ‘legs’.
When you have finished your model should look like the
drawing to the right.
You can add more detail by leaving out one of the rectangular
panels in the ‘head’ and placing some string inside to
represent the DNA.
Your finished
model should
look like this