I had the following understanding (now after reading a popular science article seeming wrong understanding):
DNA in (regular) cells (in human and some other organisms) are protected by telomers. Telomeres are shortened at each division. When telomeres reach zero size, nucleotides of the ends of DNA become "stripped" so that the DNA shortens a little. The shortened DNA does is not fully functional. This leads to aging of the organism.
But in a popular science article I've read that telomeres however shortened seem not to reach zero length. So the DNA nucleotides at the ends of DNA are never stripped. However shortening telomeres leads to the cell to become not divisible or even death of the cell.
So two related questions:
Are coding/regulatory nucleotides (not just telomeres) at the ends of the DNA ever stripped as a result of aging?
If they are not stripped and so the DNA itself is not damaged, how shortening telomeres may lead to aging? That is how aging can be caused by just shortening telomeres which however do not reach zero length?