Question

The DNA copying enzymes have a hard time working to the end of achromosome. For circular chromosomes this is not a problem, sincethere is not a sharp 'end'. However, for a linear chromosome,without extra mechanisms in place, a bit of DNA is lost off the endof the chromosome after each replication. Because of this,eukaryotes have a telomere to cap off their chromosomes.

In most cells of a mutli-cellular organism, this telomere isslowly worn away after each reproduction leading to apoptosis.Cells that need to reproduce indefinitely such as germ and stemcells have to invest in extra mechanisms to replenish the telomere.For multi-cellular eukaryotes I can see how this might be usefull(for instance as a cancer counter mechanism). However,multi-cellular organisms evolved from single-cell eukaryotes.

I cannot see a reason for wanting apoptosis in a single-cellorganism. However, single cell eukaryotes (say yeast) still havelinear chromosomes with telomere caps. What advantage did linearchromosomes provide single-cell eukaryotes to offset the extrainvestment in reparing the telomere?