... and then THAT individual, or descendants to whom that 'info' was passed, may have the ability to 'resist something'. It was discovered that some individuals, no matter the level of exposure to HIV/AIDS, did not contract the disease. Eventually, (to put it in very simple layman terms) it was discovered that they had a mutation that changed the surface structure of their cells, which meant that the virus was not able to 'latch on' so easily to the 'bits that were missing' due to the mutation... 'survival of the fittest' in a sense...

No Steve, don't beat me for using that term .... I was just trying to lay out the chain of causation simply ...