In article , Rodger Whitlock
writes
On Thu, 5 Aug 2004 13:50:40 +0100, Kay wrote:


But there isn't any genetic variability, surely? So you're not selecting
in that sense if you propagate vegetatively? In other words, even if
chose a runt you could reverse the process with a few seasons good
feeding, or vice versa. Or has Lamarckism come back into favour since I
was last on the fringes of evolutionary study?

There is some genetic variability, if I can trust my reading.
Some authors claim quite a lot, but I have my doubts about that.
(I've seen serious claims that the genetic variability among the
twigs of one apple tree is comparable to that among a similar
number of seedlings of the same apple.)

Doesn't that make a mockery of vegetative propagation of garden
varieties?

And genetics is a pretty complex subject. The ordinary Mendelian
genetics we all know and love is really only a first
approximation or broad-brush picture; there are lots of details
that transcend that model, including mechanisms for selective
activation and deacivation of genes. Since garlic is vegetatively
propagated, it's easy to imagine that these mechanisms may
influence the behavior of progeny. [Don't as me for details: I am
treading water here.]

OK - well, I'm at the first-base level of reading how DNA is replicated
during cell splitting so each cell has a copy of what was in the
parental cell. Where is the variability coming from? Mistakes in
copying? Selective activation and deactivation? Both?

Isn't selective activation and deactivation different from genetic
variability - ie the two bits can be genetically identical but have
different genes expressed?


--
Kay
"Do not insult the crocodile until you have crossed the river"