Retroviruses

[NamesAreHardToPick]

An evolutionist said this in defense of evolution:

Certain types of viruses are able to insert their DNA or RNA into the host DNA. These types of viruses are called retroviruses. By doing so, they are able to take over the machinery of the host cell to make more virus particles. Retrovirus DNA is made up of various genes including an integrase which inserts the viral DNA into the host genome, an envelope gene which makes the outer protein coat of the virus, and various other genes necessary for reproducing viral particles. Also, on each end of the virus are sections called LTRs, or long tandem repeats. These are long stretches of a repeated sequence of DNA. All retroviruses have these characteristics.

A retrovirus has a particular mode of insertion. Different viruses tend to insert into different parts of the host genome. HIV, for instance, prefers to insert into areas with active host genes. These sites, called integration sites, are abundant within the host genome for each virus, numbering anywhere from 500 to 2,000 integration sites per host genome. Also, each integration site is usually between 100,000 to 250,000 DNA letters long (letters being the A, G, T, and C of the genetic code)([url="http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pubmed&pubmedid=15314653"]http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pubmed&pubmedid=15314653]Reference[/url]). Taking the low number of 500 and the lower size of 100,000, this limits retrovirus insertion to about 50 million bases in the genome. This would mean that we could expect that one letter of DNA would be used twice every 50 million insertions. [url="http://www.pubmedcentral.nih.gov/picrender.fcgi?artid=509299&action=stream&blobtype=jpg&blobname=pbio.0020234.g001.jpg"]http://www.pubmedcentral.nih.gov/picrender.fcgi?artid=509299&action=stream&blobtype=jpg&blobname=pbio.0020234.g001.jpg]This figure[/url] shows 3,000 insertions by three different retroviruses. As you can see, the retroviral insertions are spread over all of the chromosomes in a random pattern. Not one nucleotide is used twice. There has never been a retrovirus that has been shown to insert at the same letter in the host genome even 0.001% of the time.

An analogy that helps me to visualize this process is an unabridged dictionary. Let’s pretend that each letter of the dictionary (the A’s, B’s, etc.) represent a different chromosome. Let’s also pretend that each letter in the dictionary represents a letter in the DNA sequence of the host genome. Now, close your eyes and flip through the pages. Randomly stop on a page, keeping your eyes shut, put your finger down on the page. Open your eyes and record the page number and the letter that you put your finger on. Next, pass the dictionary to someone else and have them repeat the procedure. What are the chances that you would both put your finger on the same letter on the same page? I would think this event is highly unlikely, almost like winning the lottery.

However, not all insertions go well for retroviruses. During rare events only part of the viral genome is inserted which prevents an infection of the cell. What results is a cell that is not killed by the virus and a partial viral sequence permanently implanted into the host genome of that cell. If this rare event happens in an egg or sperm, it is possible that that egg or sperm could be involved in the production of an offspring. As you can imagine, the odds of sperm or egg used in reproduction with a partial viral genome are quite low, but given enough time it does happen. What results is an organism with a partial viral sequence, called an endogenous retrovirus (ERV), present in every cell of their body including half of their eggs or sperm. Think of it as a scar left in the genome that is passed on to the next generation when it occurs in an egg or sperm.

Now we have a sequence that is part of the genome and is passed on from generation to generation. After numerous generations we look for ERV’s in people’s genomes. What we find is that certain people share the same insertion at the same spot in the DNA sequence, that is at the same letter of DNA. How do we explain this? The most obvious reason is that they share a common ancestor. Why don’t we ascribe this to two different viral insertion events? Remember that 1 in 50 million odds of two viral insertion happening at the same letter of DNA from above, and the dictionary example? This is where these come in. The odds of an effective viral insertion occurring at the same letter of DNA in two different infections is 1 in 50 million, and this is for your run of the mill, full blown, cell killing infection. What we are talking about now is a rare event of a viral misfire. Not only that, but a misfire that happens in an egg or sperm, and even more improbable a misfire in an egg or sperm that leads to a living offspring who themselves reproduce at a later time. This multiplies the chances of two people having the same ERV at the same letter of DNA due to separate viral insertions as being highly, and I mean highly, unlikely. Therefore, we can conclude that they share something like a great, great, great grandparent.

What happens when two different SPECIES share the same ERV at the same letter of DNA? The very same logic applies. Given the improbable event of two separate infections leading to the same ERV the most likely scenario is that the two species share a common ancestor. Taxonomy, through the study of fossils, has come to the conclusion that apes and humans share a common ancestor. Therefore, knowing the implications of ERV production, we should find ERV’s at the same letter of DNA in each of these species. This is a prediction made by the theory of evolution. Not only that, but the patterns of similarities should also match cladistics. Cladistics is what many call “the tree of life” which show species branching off from one another. One such clade, constructed through the study of fossils, proposes that humans, chimps, gorillas, and orangutans all share a common ancestor. The first species to branch off were orangutans, the second were gorillas, the third were chimps, and the final branch resulted in humans. This allows us to make some very precise predictions. If humans and orangutans share a common ERV at the same letter of DNA, then chimps and gorillas should also have that same ERV at the same letter of DNA because all of these species share one common ancestor. Since orangutans branched off before the other three, we should see ERV’s occuring after this branching. That is, there should be ERV’s common between gorillas, chimps, and humans that orangutans do not have. Since gorillas split off next, we should see ERV’s shared between chimps and humans that are not seen in gorillas or orangutans. In fact, there are seven ERV’s between humans and chimps that can only be explained by common ancestory, as well as the other ERV’s shared by humans and other apes.

Okay, any good information on this? Any Creationist want to take a shot at refuting it?

 

[MatthewDiscipleofGod]

Places I would start researching is:

Did God make pathogenic viruses?

Junk DNA:evolutionary discards or God’s tools?

Endogenous Retroviruses

 

[NamesAreHardToPick]

Okay thanks