On Mon, 15 Aug 2005, tomatolord wrote:

How is it possible for the DNA of corn plant to "spread" to the dna of a
weed?

It's basically the same concept as DNA spreading between different kinds
of bacteria, I think -- instead of the DNA being part of a long string of
chromosomal DNA, it floats around inside the cell on a little circle of
DNA (plasmids). This stuff can be passed between cells & even to other
[sufficiently similar] organisms because it can be small enough to get
past the anti-alien-DNA mechanisms.

In many plants, _Agrobacterium_ species bacteria can often be used to
transfer new DNA into a plant via a cut or wound in the plant. Since these
guys form little tumor balls on the roots of many plants, they could
potentially grab DNA from one plant and trasnfer to another.

Let's see... pollen was already mentioned as a possibility. A different
kind of infective plant virus or bacterium could transfer the genes
(especially viruses -- some of them are particularly good at picking up
genes from an organism and donating them elsewhere)... Some people think
that when root cells are sloughed off into the soil, soil microorganisms
could take it up.

Anyway-- basically, intraspecies pollination is really easy, some of the
other mechanisms are less likely. Doesn't mean they couldn't happen.

For a more technical description, see:
http://www2.dupont.com/Biotechnology...narrative.html