What is "transgenic?"

[CZroe]

I've heard it described as such:

A pig becomes infected with an avian flu and a human flu which creates a new strain of an avian flu which can infect humans. There was a newspaper article I read earlier this year or late last year (Just before the SARS scare) describing the outbreak in China as only being transmittied from animal to human but not between humans. The article said that the virus could "breed" with a human virus and gain the ability to jump between human hosts. It's ridiculous to say a microscopic and genderless organism can "breed," right? I thought it was some huge find a couple years ago when it was announced that the Staph bacteria could exchange DNA somehow yet now these articles are just assuming virii can do the same?

 

[Matthias99]

dictionary

You usually hear the term applied to research animals who have had genes spliced in from other species (such as humans to produce protiens or drugs, or jellyfish so that they glow in the dark, etc.). I suppose it could also apply to a disease that had spread across species (like SARS and AIDS are theorzied to have done).

It's ridiculous to say a microscopic and genderless organism can "breed," right?

Well, bacteria are microscopic and genderless organisms that can and do reproduce both asexually and sexually. That's how you wind up with "superbugs" that are immune to lots of different drugs. However, I think you're trying to talk about viruses in particular here.

Viruses can and do mutate (some of them rapidly, such as influenza and the common cold), but I'm not sure that anyone has shown them capable of exchanging genetic information with other strains of the same virus. I don't follow this sort of research really closely, though.

 

[Furor]

Transgenic is a term used to describe a species or some dna that has had another species or organisms genes (dna) spliced in with its own. An appropriate example would be a tomato plant that has had dna from a jellyfish spliced into it (like Matthias explained), so that it glows in the dark. Viruses can be transgenic because sometimes when they infect a host, they abduct part of its genome. Transgenic viruses are altered in different ways, depending on what dna they take up from their host. Sometimes doing this can cause them to be less virulent to other species or hosts, as may be the case in this example.

Bacterial breeding is just exchange of dna from one to another. There are "male" and "female" bacteria, but that only describes their genetic makeup. They're basically the same otherwise. Viral breeding may be similar to bacterial. We can't be sure here of the mechanism because we don't have specifics. Immunity of bacteria to different drugs can be carried by a virus, which can infect and insert itself into bacteria, bringing with it the immunity. Mutations also create antibiotic immunities. I haven't heard of viral breeding either, but it doesn't seem impossible.

 

[Mark R]

Viruses are nature's genetic engineers - The process of infection works as follows: The virus inserts DNA and various proteins into the cell. With assistance from the viral proteins the viral genes are spliced into the host DNA. Under instruction from the new DNA, the host cell is now turned into a virus making machine - making dozens of copies of the viral DNA and packaging them up as new viruses. In fact viruses are the main tool of genetic engineering scientists - they viruses and alter the DNA to remove the viral genes and insert their own genes. The virus is still able to infect, but without the viral genes the cell retains its normal function and does not produce new viruses.

There are a number of mistakes that can occur during this process - the daughter viruses may contain pieces of the host DNA, which will in turn get incorporated into cells infected by the daughters. If a cell gets infected with 2 different viruses (especially if they are 2 similar viruses), then the viruses may be packaged with genes from the other. In the case of flu there are 2 main genes are different between strains, and which determine infectivity and immunity. The different versions do the same job in all the viruses, and if by accident the genes are exchanged, then you essentially have a new strain of virus, which can still do everything it needs to survive - and to which the population may not have immunity, and may be able to infect different species.

Bacteria, too, can exchange DNA - some are able to absorb DNA from the environment, viruses may cause transfer of DNA between different bacteria (viruses do infect bacteria as well), there are even some pseudo-sexual bacteria (where the presence of a gene allows that bacterium to attach to another and transfer in a copy of the DNA for that gene - sometimes, some other genes can be transferred at the same time).

 

[rjain]

if they can both infect the same cell, they may have a chance to "breed". the key is that there is an intermediate host which can be infected by both strains.

 

[CZroe]

Originally posted by: rjain
if they can both infect the same cell, they may have a chance to "breed". the key is that there is an intermediate host which can be infected by both strains.

I thought of that after posting the question. Can that happen? I mean, could two identical virii ever infect the same cell? Seems like there would be ways to prevent this as it would be somewhat wasteful.