2
$\begingroup$

Hey there everybody !

I know that viruses show only one living feature - Reproduction. However they cannot reproduce by themselves so on this basis they cannot be classified as living organisms. They need a host cell to reproduce.

When a virus infects a host cell... and injects the DNA into the host cell... and the DNA merges with the nucleus of the host cell and the host cell starts creating new viruses.

Now my question is, when a new virus is 'made' will it be made in its full size ? Like- will the virus which is made by a host cell be an 'adult'/mature virus ?

In other words will a newborn virus be like a newborn human baby, where the baby has to grow up to become an adult. Does a newborn virus have to grow ?

I assume NOT, since Viruses don't have any organelles to do any growth and development.

But can somebody confirm this ?

Because there is a weird image in my textbook where we have a virus infecting a bacteria cell and the next image there are 'baby' viruses inside the bacterial cell.

Thanks in advance

$\endgroup$
2
  • 1
    $\begingroup$ Not all viruses are DNA, and not all DNA viruses integrate their DNA into the host cell. $\endgroup$
    – swbarnes2
    Aug 27, 2021 at 18:01
  • 1
    $\begingroup$ Please clarify your specific problem or provide additional details to highlight exactly what you need. As it's currently written, it's hard to tell exactly what you're asking. $\endgroup$
    – Community Bot
    Aug 27, 2021 at 18:35

3 Answers 3

4
$\begingroup$

Viruses do not grow. Instead, their components self-assemble inside of a cell to form complete new viruses, which are then released to go and infect more cells.

Here is a fairly accessible review on the subject: Mechanisms of Virus Assembly. Basically, when the virus reproduces, it manufactures a bunch of parts. A typical virus may be thought of as having three types of part:

  • The genome (RNA or DNA) that encodes for the virus
  • Structural proteins ("SPs"), which form the packaging for the viral genome
  • Non-structural proteins ("NSPs"), which handle operations within the cell such as replication, packaging, and suppression of host cell anti-viral responses.

In the replication process, the virus makes a bunch of copies of each of these independently. The SPs and genome come together to form new viral particles, and the NSPs get left behind. Consider for example, this Sindbis virus genome:

  • Bases 79..7635 encode a "non-structural polyprotein": a collection of four protein elements that assemble in various different configurations to build a "viral factory" out of membranes within the cell and then copy the genome.
  • Bases 7681..11418 encode a "structural polyprotein" collecting together the five elements that form the capsid that self-assembles around the genome to make a new particle.

Now, this is biology, so there are exceptions and blurry boundaries, but this covers the typical cases pretty well, and even in the non-typical cases I have never heard of a virus that "grew" in a meaningful way.

$\endgroup$
3
$\begingroup$

Short answer - no, they don't grow once they are released from the cell.

I like to think of it as a factory production process. The widgets coming out of the factory assembly line don't grow, they just get sent out. Sometimes the assembly line makes mistakes and a virus might be missing something (or most things) or might even be just an empty shell and so be smaller. Some viruses are contained in "bags" (enveloped viruses), so sometimes the bag might be defective instead, or even empty. Some viruses (like TMV) "self-assemble" with their protein coat automatically "growing/assembling" around their nucleic acid (RNA in this case), but that's a one-time process in the cell and doesn't continue once the virion is released.

$\endgroup$
3
$\begingroup$

I agree with the answers given by @jakebeal and @Armand. However, the analogy between a newborn virus and a newborn baby, suggested by the OP, is not without its merits. Indeed the virions released by a cell, in which the virus has replicated, are not always ready viruses. They need to undergo the process called maturation. E.g., see here and here.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.