Science Buddies: "Ask an Expert"

So i understand the function of DNA in other cells, but for the virus, it doesn't make much sense to me. It's not for ribosomes messengering right? So then what is its function in the virus. Is it used to inject into other cells to spread illness? Please help.

Hi, Curiouskid!

What project are you considering? I found two on the sciencebuddies.org that deal with viruses:

https://www.sciencebuddies.org/science- ... background
https://www.sciencebuddies.org/science- ... p029.shtml

The answer to your question will depend on the type of virus. They don't all work in the same way. Wikipedia has some general information on the types of viruses and links to other pages that may help you with your research.

http://en.wikipedia.org/wiki/Virus_classification

Let me know if I can help you further.

-Lisa

Hi curiouskid,

DNA serves to encode genes that the virus needs to complete their life cycle within the host cells. In a sense, it's not very much different from the purpose that DNA serves in other cells--DNA contains genetic information that encodes for molecules and proteins that are important for development and function. Depending on the virus, DNA can be delivered to the host cells in different ways. If you're looking at bacteriophages (viruses that infect bacteria), phages attach to the bacteria and then inject their DNA into the bacterium. For viruses that infect eukaryotic cells, the viral DNA is often protected by a protein shell called a capsid. Once the virus is taken up by the host cell, the capsid will be uncoated and the DNA will be released into the host cell.

A virus is actually not a living organism even though it has its own genetic information. This is because viruses don't have their own translation and protein synthesis machinery to turn the genetic information encoded in their DNA into actual molecules and proteins. Because of this, viruses need to infect host cells because host cells have all of that machinery available. Hence, viruses essentially "hijack" host cell machinery in order to make viral proteins, replicate their DNA, and then package the proteins and replicated DNA into individual viral particles that are then released from the host cell. These viral particles can go on to infect neighboring host cells or can be shed from the host to be transmitted. Pretty remarkable for something that is actually not alive!

A virus has no conscience--their DNA just encodes for information needed to produce proteins that allow the virus to replicate, survive, and to be transmitted, and is not intended to cause "illness" per se. Sickness and disease is often a side effect or unfortunate outcome of the virus undergoing their life cycle within the host (for example, some viruses need to lyse their host cells so that new viral particles can be released out of the host cell, and sometimes, extensive killing of a certain host cell type may result in damage and disease).

Hope that clarifies things a bit. Let us know if anything is confusing or if you have more questions!

Connie

For the sake of scientific accuracy I would like to point out that not all viruses have DNA as their genomic material and this is a very important distinction because it has a major effect on their biology.

Retroviruses such as HIV contain single-stranded RNA--not double-stranded DNA. They do use a DNA intermediate, however, although that is not what the virus contains--the DNA is made by an enzyme called reverse transcriptase AFTER the HIV infects a host cell.

Other viruses like respiratory syncytial virus, the RSV that causes bronchiolitis in infants, contain single-stranded RNA that is transcribed into a positive sense message from which viral proteins are translated (https://microbewiki.kenyon.edu/index.ph ... tial_virus).The dreaded Ebola virus is also an RNA virus.

Just wanted to keep the record straight...

Sybee

Yup, that is one thing I forgot to mention--that some viruses have genetic information encoded in the form of RNA. Thanks for clarifying!