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nafex - Re: [NAFEX] Cloning

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  • From: list@ginda.us
  • To: North American Fruit Explorers <nafex@lists.ibiblio.org>
  • Subject: Re: [NAFEX] Cloning
  • Date: Sun, 30 Mar 2003 12:09:11 -0500


On Sunday, March 30, 2003, at 11:35 AM, Keith Benson wrote:



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?


Does the cellular clock in plants, specifically pome fruits include scenesce genes? If not then the thing would essentially go on until random mutations eliminated all of the cultuvars - and that could take a while - especially with people culling off types (eliminating mutations).
There are those who even argue that there are some vertebrates that do not become scenescent (larger turtles and tortoises for example). Not everyone may be pre-programmed to fall apart.

Keith



In general, plant cells are not programmed to age and die (what Keith calls "senescence"). Plants tend to have lots of undifferentiated cells that are capable of becoming whole new plants, only different from the original plant due to random genetic damage. Most animals are different. Each of our cells is programmed to reproduce a fixed number of times and then die. The only exceptions are new gametes and cancer cells. (Cancer cells all have damage to the part of the genes that says "die now".) There is something in a newly fertilized eggs that "resets" the clock, or it may happen earlier, when the germ cells that combine to form the fertilized egg are formed. That's why people were watching Dolly for signs of premature aging - no one really knows what it takes to reset the clock. (That's also one reason scientists are mostly more interested in fetal stem cells than adult stem cells - fetal stem cells still have a lifetime of reproduction in them.)

In simple terms, every plant cambium cell is similar to an animal fetal stem cell. (Except the cambium cells are designed to turn off at a fixed time.)

Ginda




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