Hi judge,
quote:
The similar mutations happen in independent lines of the gene in the virus and yet these mutations are selected for during the life of the macaque?
If I understand this correctly ..how long does it take for these muations to be selected for?
What you have to keep in mind is that the viral lifecycle is not the same as its hosts. The virus infects the macaque and if an active infection is established, you will have thousands of generations of virus occuring in the infected individual..meanwhile each host represents a single generation. So a lot more evolution is occuring in the virus relative to the monkey. And in the case of retroviruses like SIV, they have a really error prone reverse transcriptase so they produce massive numbers of mutated viral copies on which the hosts defenses select against. But with such a massive population size potential and so much variation, you will almost always stumble accross variants that have an advantage (that is why so many single drug treatments against HIV fail..a variant arises that is resistant and becomes frequent). The constraints on the env gene mean that mutations outside these specific residues for the most part have been selected against, not that they do not occur. If a mutation deletes the transmembrane domain, the virus is dead. Thus they converge, even independently, on a few specific mutations even if the infection was in different individual monkeys. The dead copies (well not all inactive or so dead) of viruses often show up in our genome such as human endogenous retroviruses (HERVs) which often show key deletions for example, most lack the env gene entirely so they have lost the ability to escape the cell and cause active infection.
Assigning a specific time until selection occurs would be near impossible given all the variables. It would vary from individual to individual since our own host defenses are themselves variable.
Hope this helped.
Cheers,
M
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