Viruses

sillybird

Apologies if this is the incorrect place to start this threat. I'm finding it difficult to understand Viruses are they alive or not?? I think many Scientists would give diff answers. Anyways I'm in the final stages of finishing a project and would appreciate anyones thoughts on the following:

Viruses may have influenced the evolutionary transition from prokaryotic to eukaryoric cells. How might this be explained?
What evidence suggests that viruses have a major impact on evolution? Would this be similar to below?
An instance in which viruses could be involved in lifesaving gene therapy? My thoughts on this is if the nuclear DNA of a cell is destroyed a virus can take advantage of the dead cell and bring a cell back to life. A virus uses it genes to rebuild the cell. Would this be correct.

Many thanks for any replies.

MatthewVII

sillybird wrote: »

An instance in which viruses could be involved in lifesaving gene therapy? My thoughts on this is if the nuclear DNA of a cell is destroyed a virus can take advantage of the dead cell and bring a cell back to life. A virus uses it genes to rebuild the cell. Would this be correct.

Many thanks for any replies.

Not quite what gene therapy is about. From what reading I've done, gene therapy is used to treat inherited genetic conditions which cannot be treated by conventional means since the way the body works is fundamentally defective. A good example of this would be Cystic Fibrosis, where an abnormal chloride channel gene means that fluid secretions throughout the body are viscous and block the ducts that secrete them.

Gene therapy takes advantage of the fact that the way viruses replicate is by attacking a cell and inserting it's own DNA into the cell's genome. The cell, thinking this is its own DNA, uses the material to create proteins of viral origin. This results in the synthesis of more virus particles and when the cell has produced a certain amount, it bursts, dies and releases them.

The idea is that by manipulating a virus, you can change its DNA into the DNA that is defective in a Cystic Fibrosis sufferer. Thus, when the virus attacks the body's cells, instead of inserting its viral DNA it'll insert a healthy copy of the gene which CF patients are deficient in. This means that the cell will start making normal proteins and hopefully improve the body's function to act more like that of a healthy person.

You can sort of think of viruses as hijacking cells and cell machinery to reproduce itself. If we can get to the virus before it infects a cell and change it so that instead of making more of itself it produces something useful then we can hopefully help the patient get better

That's just a very simplistic way of explaining. Sorry I don't know much about viruses and evolution

sillybird

Thanks a mill Mathew that really makes so much more sense to me now.

I'm dumbfounded by virus evolution after a month googling I said I put a thread here and see what are the thoughts it. There doesn't seem to be a clear answer or understanding out there in anything that I've read!

MatthewVII

sillybird wrote: »

I'm dumbfounded by virus evolution after a month googling I said I put a thread here and see what are the thoughts it. There doesn't seem to be a clear answer or understanding out there in anything that I've read!

Well from what I've read about the process of Endosymbiosis, simple prokaryotic cells became eukaryotic by phagocytosis (enveloping and consuming) other organisms. Sometimes they found that when these organisms worked alongside them, they could work more efficiently. A good example of this is the mitochondrion, which is a believed to be a bacterium which was engulfed by early cells. These cells found that mitochondria enhanced the efficiency with which the cells themselves could utilise energy so they kept it around and gained a survival advantage because of it. This is why mitochondria have their own DNA and DNA transmission seperate from the rest of the cell.

As to where viruses come into it, the theory is that viruses greatly resemble a eukaryotic cell nucleus - the arrangement of DNA, division of RNA transcription and translation etc. This led researchers to theorize that eukaryotic cells are former prokaryotic cells which swallowed a large virus. The virus then "took control" of the cell with it's own proteins and DNA. over time it developed more and more complex and finely tuned methods of controlling the biochemical processes within the cell and resulted in the highly regulated structure we see today with the former virus as the nucleus controlling its activity

sillybird

Thanks Matthew I was just about to post that I was reading an article from Scientific Americia that the nucleus of an eukaryotic cell may have developed from a virus that made a permanent home within a prokaryotic cell to see your thoughts! Hard to believe!!

MatthewVII

sillybird wrote: »

Hard to believe!!

Yeah, it's fascinating stuff! I wish I had more time to read about these things.

sillybird

Absoutly - I'm doing a Foundation Science course in NUI Galway with the intention to go on and do a degree course in Sept as a mature student. Yikes!! Have to say I'm realy excited about learing - biology in particular.

I'm reading Essential Biology by Campbell, Reece, Simon to say the least its quite facinating.

Thanks so much for all your help realy appreciate it.

DrIndy

Evolutionary biology is truly fascinating - i wish i had more time to read into it than i do now.

Please keep the posts coming!

sillybird

It truly is DrIndy...I wish I knew more about it to post info!

sillybird

sillybird wrote: »

Absoutly - I'm doing a Foundation Science course in NUI Galway with the intention to go on and do a degree course in Sept as a mature student. Yikes!! Have to say I'm realy excited about learing - biology in particular.

I'm reading Essential Biology by Campbell, Reece, Simon to say the least its quite facinating.

Thanks so much for all your help realy appreciate it.

Oh god, when I did first year biology, I hated Biology,why were we studying Hydra?
I think the course has changed since I did it.

AtomicHorror

MatthewVII wrote: »

As to where viruses come into it, the theory is that viruses greatly resemble a eukaryotic cell nucleus - the arrangement of DNA, division of RNA transcription and translation etc.

I'm not sure that theory holds. The nucleus is a structure which does transcription inside the nuclear membrane. I know of no virus capable of doing transcription by itself. Also, the nuclear membrane is just that, a membrane. And whilst many viruses have a membrane-like envelope, this usually surrounds a protein shell which our nuclei do not posses. Our nuclei are also huge by comaparison even to quite large viruses (viruses are about 1000 times smaller in diameter). Perhaps most importantly, the genome capacity of most viruses is minisucle next to that of eukaryotes (viruses manage 10 thousand to 100 thousand DNA or RNA bases whilst a human nucleus contains 6 billion bases if it is diploid).

There is one point in it's favour though. Our genomes are arranged into bundles- chromosomes. I don't know of any prokaryotes that do that, but I I do know of viruses which do it. It's one of the reasons why the influenza virus is so adaptable.

MatthewVII wrote: »

This led researchers to theorize that eukaryotic cells are former prokaryotic cells which swallowed a large virus. The virus then "took control" of the cell with it's own proteins and DNA. over time it developed more and more complex and finely tuned methods of controlling the biochemical processes within the cell and resulted in the highly regulated structure we see today with the former virus as the nucleus controlling its activity

It seems like it could have been a prokaryote either, since they have more of the traits we'd associate with a nucleus. Bigger genome capacity, the capacity to expand, the enzymes needed to to perform transcription within the membrane. I can see where you're going with the virus slant, they'd be better suited to hijacking the machinery already present in the cell. The big question is what was in the cell prior to the phagocytosis event. Presumably some non membrane bound genome that has since been lost or exapted.

The prokaryote idea holds more water for me because we can see other examples of it. Our mitochondria were once free living, and the chloroplasts in plants were some form of photosynthetic prokaryotes. We do know that parts of our genome are derived from viruses, but as a result of insertions.

The more I think about the virus idea though, the more I can imagine how it might have worked if enough time were allowed... It's quite a fascinating spin on the endocytosis bit. Do you have any links on the hypothesis?