https://barryhisblog.blogspot.com/p/integrase.html
Integrase is the key to understanding what people call "ERVs" and what they tell us.
In shall try to keep this as simple as possible and use the minimal, least technical words possible.
But keep your eye on critical importance of integrase.
I used the acronym, 'ERV' above. I wouldn't normally use an acronym first off, without saying what the letters stand for, but they mean 'Endogenous' 'Retro' 'Virus'.
Let's go through those words backwards.
Pretty well everyone knows what a virus is. It is not a bacterium, but minimal particle that is capable of invading our bodies and causing us to contract viral diseases. The common cold virus is an example. So is the 'flu.
Now stay with me through a couple the harder, but unavoidable bits.
The 'retro' bit refers to a special type of virus - one that carries it genetic information in RNA form and 'reverse transcribes' it into the equivalent DNA form. The information involved goes in the opposite, 'retro' direction as usual.
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| Transcription and reverse transcription |
The viral information, now in its DNA form, can exploit the target host cell's machinery over and over again by making it produce new RNA copies of itself over and over again.
This is retroviral infection, an example of which is AIDS (autoimmune deficiency syndrome) is caused by the retrovirus, HIV (human immunodeficiency virus).
An important note to make is that it is integrase that is the viral element that does the cut and paste of the entire virus into the host DNA when it infects (integrates with) it and it cannot target where it does so.
So we have hosts with retroviral integrations in any old position, going from the DNA of one cell to another.
And not all cells are infected.
These are the signals of horizontal infection - catching a virus from the environnent.
But then we have hosts with retroviral integrations in exactly the same locations, going from cell to cell and, are present in every single cell.
This is the signal of vertical transmission. The viral DNA has been copied from the DNA of the first cell the host began its life with. It is the ony explanation that fits the facts. A retrovirus has integrated with the DNA of an egg or a sperm cell in one of their ancestors and all the resultant cells inherit it too via normal cell reproduction. As it is a part of its genome, we call it endogenous, or 'in the genes'. These are the ERVs.
Now, when we find different species with large numbers of ERVs in their genomes, in corresponding DNA locations, we can conclude that the ERVs involved descend from the common ancestors that originally acquired them. If you say "they were put where they are by design", see this page and see if you can answer any of the questions such an idea raises. https://barryhisblog.blogspot.com/p/in-science-we-apply-principle-of.html
To find out more about ERVs, go to the FAQ link at the top of any of my pages on the subject, https://barryhisblog.blogspot.com/p/endogenous-retroviruses-frequently.html
The viral information, now in its DNA form, can exploit the target host cell's machinery over and over again by making it produce new RNA copies of itself over and over again.
This is retroviral infection, an example of which is AIDS (autoimmune deficiency syndrome) is caused by the retrovirus, HIV (human immunodeficiency virus).
An important note to make is that it is integrase that is the viral element that does the cut and paste of the entire virus into the host DNA when it infects (integrates with) it and it cannot target where it does so.
So we have hosts with retroviral integrations in any old position, going from the DNA of one cell to another.
And not all cells are infected.
These are the signals of horizontal infection - catching a virus from the environnent.
But then we have hosts with retroviral integrations in exactly the same locations, going from cell to cell and, are present in every single cell.
This is the signal of vertical transmission. The viral DNA has been copied from the DNA of the first cell the host began its life with. It is the ony explanation that fits the facts. A retrovirus has integrated with the DNA of an egg or a sperm cell in one of their ancestors and all the resultant cells inherit it too via normal cell reproduction. As it is a part of its genome, we call it endogenous, or 'in the genes'. These are the ERVs.
Now, when we find different species with large numbers of ERVs in their genomes, in corresponding DNA locations, we can conclude that the ERVs involved descend from the common ancestors that originally acquired them. If you say "they were put where they are by design", see this page and see if you can answer any of the questions such an idea raises. https://barryhisblog.blogspot.com/p/in-science-we-apply-principle-of.html
To find out more about ERVs, go to the FAQ link at the top of any of my pages on the subject, https://barryhisblog.blogspot.com/p/endogenous-retroviruses-frequently.html
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