|Can a virus reproduce without the presence of
|Question Date: 2017-11-30|
Viruses are defined by their need to reproduce
in another organism, so the answer is no.
It takes a lot of cellular machinery to
reproduce. By measuring the number of genes, we
can get a sense of how much machinery is required
for a cell to reproduce and survive.
Scientists think that there are around 250
genes that are required for a living cell.
However, in nature, the smallest genome of a
non-parasitic bacteria is 1,389 genes.
Therefore, just to have an organism reproduce
by itself requires over 1000 genes. In contrast,
most viruses have far fewer genes, with the
smallest viruses only have a few genes.
There are actually a few viruses with genomes of
over 1000 genes, but they still can’t reproduce by
themselves. If these large viruses could reproduce
by themselves, then they would no longer be
The answer is no! This is what makes
viruses one of the most interesting and curious
things in our world. If they are not in a host
cell, they are lying dormant on whatever surface
they may happen upon. That means each
specific virus has an specific life span outside
of a host. A virus, like the retrovirus human
immunodeficiency virus (HIV) cannot survive very
long outside of a host (hours) , but the small
pox virus can survive for up to 2 years!
Sadly, this was exploited by the British in
their war against the indigenous Americans as a
biological warfare agent. They let people
infected with smallpox infect blankets and other
items, which they then gave to the tribes as
"gifts". Take a read on this Wikipedia page if
you want to learn more about that incident!
killing the native americans
No, and this is part of the definition of a virus:
viruses do not contain the information
necessary to build all of the enzymes and other
stuff necessary to replicate DNA. Living cells
do have all of this information, and in order to
reproduce, the virus must co-opt the enzymes of an
existing living cell. This is why viruses are
only sort-of alive.
A virus cannot reproduce without a living
cell It must have a living cell to be able to
replicate itself. The virus contains the bare
minimum - DNA that encodes for its proteins
and a small amount of its own proteins. This is
then injected into a living cell (bacterial or
eukaryotic) where the viral DNA (or RNA) is then
reproduced, transcribed, translated and new virus
particles are made. The virus is interested in
replicating and producing more of itself but it
cannot do so without the presence of another
Viruses cannot reproduce without a host,
because viruses do not have all the parts needed
Viruses all have the blueprint of
reproduction, either as DNA or as RNA. They all
have a protein coat that protects the DNA or RNA,
but they do not have other proteins or RNAs like
living cells do. After viruses infect their
hosts, they can hijack the host replication system
to multiply. Some viruses, though, can survive
a long time without hosts.
No. A virus can't reproduce outside a living
I'm now flying home from a conference about the
origins of life and astrobiology; and one of the
speakers said they think viruses formed and
infected cells soon after there were cells to
Viruses also carry DNA from one cell to
another, which is called Horizontal Gene
Transfer - HGT.
This is a really interesting question because
it points out some important differences between
viruses and cells.
We know that cells can reproduce through the
process of mitosis but can viruses do that
too? It turns out that they cannot.
They are missing a few important structures that
would allow them to reproduce. One of which are
ribosomes. Ribosomes are the structures
that translate the mRNA message into an amino acid
Since viruses do not have ribosomes they
are unable to create the proteins that are
necessary to build new viruses. They need to
infect cells and force them to create new viruses
for them. Without the help of a host cell,
viruses could not reproduce at all! This
brings up a very interesting question: are
viruses alive? What do you think? Are there any
other organisms that cannot reproduce on their
own? Thank you for your question!
I cannot think of any example of a virus that
could reproduce without another host organism. If
it could do that, then it would be
self-replicating, and that would make it alive and
not really a virus anymore.
I think of viruses more as a container with
some DNA or RNA inside. This is very similar
to a computer code without a computer or any of
the software or operating system to interpret and
run the code. The virus must borrow the
machinery it needs to read and copy its genetic
code from the host organism in order to reproduce
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