Do living organisms get old because of their imperfection...

[deltasigma]

@leahcim

But telomere length is not a hard limit at all. There is a process to regrow telemeres that is used in germ lines. If there was a really great benefit to having immortal non-germ cell lines, it could be used there as well (and as is noted, this happens in cancer cell lines). Non-germ cell lines obey the Hayflick limit because it is convenient as part of the process of forming a functional body, not because they intrinsically have to.

I don’t know what you’re talking about, but I’m talking about adult humans. Turning on telomerase in adult humans would have unpredictable results and would be a stupid thing to do.

@leahcim

Again, these transcription errors are not a problem for germ-line cells, so why would they be an insurmountable problem for non-germ-line cells?

I like to think of humans as basically single-celled organisms with immortal cell lines that periodically spawn off a colony of division-limited cells to form structures to carry the immoral cells around.

they ARE in fact a problem germ cell. Haven’t you ever read any of the studies that show that older men have more mutations in their sperm cells than younger men?:rolleyes:

[deltasigma]

FYI on the issue of mutated sperm cells for anyone who is interested

By starting families in their thirties, forties and beyond, men could be increasing the chances that their children will develop autism, schizophrenia and other diseases often linked to new mutations. “The older we are as fathers, the more likely we will pass on our mutations,” says lead author Kári Stefánsson, chief executive of deCODE Genetics in Reykjavik. “The more mutations we pass on, the more likely that one of them is going to be deleterious.”

Haldane, working years before the structure of DNA was determined, was also correct about why fathers pass on more mutations. Sperm is continually being generated by dividing precursor cells, which acquire new mutations with each division. By contrast, women are born with their lifelong complement of egg cells

[leahcim]

@deltasigma

I don’t know what you’re talking about, but I’m talking about adult humans. Turning on telomerase in adult humans would have unpredictable results and would be a stupid thing to do.

Agreed. But in fact it can be done as is evidenced by (1) cancer cells, and (2) the fact that we all start out as single cells with more-or-less full length telomeres, despite the fact that those cells are descended from quite a few generations of other cells. In fact, we even know some of the mechanism through which this happens, and that it is specifically turned off except for those cases.

If animals with immortal cell lines were selected for, they could exist. But they are not.

they ARE in fact a problem germ cell. Haven’t you ever read any of the studies that show that older men have more mutations in their sperm cells than younger men?:rolleyes:

And yet, somehow we manage to reproduce despite every single sperm and ovum being descended through a great number of generations of cells. Every germ-line cell of yours is a descendent of one of your parent’s germ-line cells, and one of your grandparent’s, and one of your great-grandparent’s, through all of human history and prehistory to a time before we were even human. Human cells, in a healthy state, reproducing indefinitely with no Hayflick limit in sight.

Biologically, telomere shrinkage is a “solved problem” which is seemingly deliberately “unsolved” in somatic cell lines, for whatever reason (probably related to the whole “cancer” thing).

[deltasigma]

@leahcim

Agreed. But in fact it can be done as is evidenced by (1) cancer cells, and (2) the fact that we all start out as single cells with more-or-less full length telomeres, despite the fact that those cells are descended from quite a few generations of other cells. In fact, we even know some of the mechanism through which this happens, and that it is specifically turned off except for those cases.

If animals with immortal cell lines were selected for, they could exist. But they are not.

OK. Not really sure of the relevance of this for the current discussion, but no objections as long as we’re off on an academic tangent.

@leahcim

And yet, somehow we manage to reproduce despite every single sperm and ovum being descended through a great number of generations of cells. Every germ-line cell of yours is a descendent of one of your parent’s germ-line cells, and one of your grandparent’s, and one of your great-grandparent’s, through all of human history and prehistory to a time before we were even human. Human cells, in a healthy state, reproducing indefinitely with no Hayflick limit in sight.

Biologically, telomere shrinkage is a “solved problem” which is seemingly deliberately “unsolved” in somatic cell lines, for whatever reason (probably related to the whole “cancer” thing).

Of course it’s solved. You get a fresh start with each new generation. The problem is that if the new generation is plagued with autism say (see my previous link), that generation is not viable (in the prehistoric caveman sense - just to be clear) so only the viable generations go on to procreate. If you consider that a “solution”, then . . . OK.