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nafex - Re: [NAFEX] Cloning

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  • From: Joe and Ellen Hecksel <jhecksel@voyager.net>
  • To: North American Fruit Explorers <nafex@lists.ibiblio.org>
  • Subject: Re: [NAFEX] Cloning
  • Date: Sun, 16 Feb 2003 13:53:24 -0500

Thomas Olenio wrote:

Hello,

What is the difference between grafting fruit trees and Dolly the cloned
sheep?

I believe part of Dolly's problem was premature aging, due to her cellular
clock being set from the starting point of a mature sheep. Yet grafted
trees do not seem to suffer the same fate.

Earlier fruiting may be tied to the advanced cellular clock of the scion,
but it does not seem to shorten the lifespan of the tree.

Anyone know the reason?


Darned good question. I don't think anybody truly *knows* the answer. I am willing to share my biases and beliefs.

I suspect that the major differences is that plant tissue is less differentiated than animal tissue. Many trees, even very mature ones, will regenerate from root cuttings. All of the normal tree parts from the roots.

One side effect of differentiation relates to the immune system. Plants do not have active immune systems like animals. They do not produce antibodies that gang-tackle foreign proteins. One of signs of aging is that the immune system winds down and our bodies become more vulnerable to infections and cancer.

I currently think that the immune system winding down is actively programmed. Our bodies are filling up with crud (protein chopped up by UV, bacteria and virus that are dormant-in-place, pre-cancerous cells that have not figured out how to sequester blood supply). The collateral damages caused by a hyperactive immune system would outweigh the benefit of destroying relatively benign intruders. As a frame of reference, the pathology of Arthritis, Lupus and Leprosy all have auto-immune components.

Another side effect relates to circulation and rate of healing. I find that as an old geezer my cuts heal much more slowly than those of children. I have no firm beliefs about "why", but it may have something to do with not triggering those pre cancerous cells into fully-blown cancer.

I write as though our bodies are constantly making rational, statistically optimized decisions. That is silly, of course. Rather, I think that those families (animal or human) that exhibited excessive healing rates or immune responses lost many members to cancer, etc. Loosing too many members makes the family fragile and they become extinct. So there is a Survivor Bias toward those family lines that have immune system coast down rates that are near optimum.

The rate of healing in plants seems to be related more to site fertility and carbohydrate reserves.

My 2 cents.



Later,
Tom



--
-Joe Hecksel
My personal web site: http://my.voyager.net/~jhecksel

"March" is Latin for "Mud". (Joke) March/Mud will be welcome when it comes







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