Jayjay

I was browsing through the talkorigins' "29 evidence for macroevolution", and a question sprang to my mind about endogenous retroviruses. According to the article, we've identified 7 shared endogenous viruses between humans and chimps, and we know that about 1% of our genome is just non-coding viruses.

My question is, how do we know that a given non-coding portion of DNA is a virus, and not something else?

Edit: :banghead: Ack, didn't notice they were discussed in another thread already...

theyeti

I guess you've found the answer already, but it's the presence of gag, pol, and env genes that define a retrovirus. And they aren't necessarily non-coding.

theyeti

Jayjay

Actually, I haven't yet found an answr. "Gag, pol and env"?

MortalWombat

Three genes found in retroviruses. Gag (short for Group specific Antigen) codes for the inner coat proteins and nucleic acid binding proteins, Pol (polymerase) codes for reverse transcriptase and integrase, and Env (envelope) codes for the viral membrane associated proteins. In addition, the protease that is responsible for processing these polyprotein complexes is either coded in frame with the end of the gag polyprotein or at the beginning of the pol polyprotein, depending on the retrovirus.

In addition to the three genes found in retroviruses are what are called LTRs, or Long Terminal Repeats; repeated sequences at each end of the viral genome.

So the typical structure of a retrovirus is:

LTR-GAG-POL-ENV-LTR

Often times, due to certain recombination events, one encounters only a single or both LTRs integrated into the host genome in the absence of the other genes.

Jayjay

Thanks!