Main content
Course: NOVA Labs > Unit 1
Lesson 3: RNA: the wonder molecule- The RNA enigma
- The RNA engima quiz
- RNA: The basics
- Protein synthesis in the cellular factory
- Protein synthesis in the cellular factory quiz
- Protein synthesis
- The RNA origin of life
- The RNA origin of life quiz
- RNA world
- Virus wars
- Virus wars quiz
- Viruses
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Virus wars
All cellular life, including you, is in an ancient and unending war with viruses. Watch how viruses attack cells and learn about RNA interference, one of the ways that cells fight back. You can play the virtual RNA game at NOVA Labs. Created by NOVA.
Want to join the conversation?
- So, if viruses are only genetic information in a protein shell (1:05), are viruses considered living things?(1 vote)
- Technically not. Fun fact-viruses ore not part of the six kingdoms of life.(2 votes)
- At2:00, it says Dicer looks for double-stranded RNA. What (besides thymine being swapped for uracil) separates this from DNA?(1 vote)
- DNA and double-stranded RNA are different because of a few molecular differences, including form and function. Double-stranded RNA is able to assume many roles, such as transporting molecules, synthesizing other molecules, and even carrying the code of life itself. RNA is a ribonucleic acid, while DNA is a deoxyribonucleic acid. The deoxy part means that on one of the ribose sugar's carbons, there isn't an oxygen atom (on the 5' carbon, I believe.)(1 vote)
- why don't viruses fight till they win the cells are they allies or neutral or do they just don't care?(0 votes)
- If you have a force of say 1000 warriors holding spears vs 10 tanks with holes, you might leave couple of warriors before the tanks patched up and blew most of your forces apart but you could get out with some food and run and destroy something else.
If you left all of them, patch up the hole and the warriors are dead.(0 votes)
- our cells dont have walls. we have membranes. why did he say this.(0 votes)
- Also some people call the cell membrane the cell wall since they both share a similar purpose.(1 vote)
Video transcript
All might seem outwardly peaceful, but right
now tiny battles are raging inside of you. The battles are being fought for control of
the molecular machinery that runs your cells and keeps them, and you, alive. Who are the attackers? They are miniscule, yet deadly, viruses. If you've ever had chicken pox, the flu, or
the common cold, your cells have fought and defeated viruses. Your cells have factories with the power to
create molecular machines. Viruses need to hijack that factory to copy
themselves because they do not have factories of their own. Each virus is like a little tank that can
blast a hole in the outer cell wall and send its forces in. These intruders change the blueprints in the
factory's headquarters so the factory starts producing more viral tanks. It doesn't stop until it builds so many tanks
that the cell bursts right open. This is what a virus attack might look like
if you were the size of a cell. Most viruses are little more than genetic
information----DNA or RNA----inside a protein shell. They bind to a cell and inject their genetic
code inside. The invaded cell treats this code as its own
and starts making virus protein components to build new viruses. When enough viruses have been assembled, they
burst through the cell membrane and the whole process starts again. Fortunately, your cells have evolved their
own defenses. When you get sick with the flu, at first the
viruses win out, but then your immune system learns to recognize and destroy the invaders. One immune response, which was only recently
discovered in plants and some animals, is called RNA interference, or RNAi. Cells make a protein called DICER. It's always on the lookout for double stranded
RNA, which is used by many viruses but rarely by cells. When DICER finds this RNA, it dices it up. DICER doesn't stop all the viral RNA from
getting through, but it doesn't need to because RNAi has a great trick up its sleeve: it uses
those chopped up pieces of RNA as weapons against the virus. Those chopped up RNAs are shreds of the virus's
blueprint for copying itself. Now, when that virus tries to hijack the cell's
factory, RNAi molecules are ready: they check all the protein assembly instructions against
the chopped up virus RNA snippets. Anything that matches is something that the
virus is trying to make, so the cell slices it up before it makes a protein. And just like that, the cell defeats the virus. RNAi is not only a great natural defensive
weapon, but also a powerful tool for biological research. Scientists can use the same basic mechanism
of RNA interference to turn off one gene at a time and study the effect on the cell and
the organism. For example, turning off one gene may drain
all of the pigment out of a purple flower. Another might prevent a plant from producing
a toxic chemical, making it safe to eat. Scientists have not yet determined whether
human cells naturally fight viruses with RNAi, but it is possible that one day we will be
able to use RNAi to deactivate cancer-causing genes and genetic disorders. Meanwhile, viruses and cells will continue
evolving ingenious weapons to try to gain the upper hand as the Great Virus Wars rage
on.