Re: RE:Hyb: Cytoplasmic inheritance was disease resistance
OK, this is very interesting stuff, but still looking for some
clarification here on the fertilization process itself, because I see some
potential confusion of expression and perception going on here. Again to
repeat Neil's question in a different way. Isn't any extranuclear genetic
material from the male gamete (if any exists) going to simply be coming
from outside the nucleus of the same male cell that fertilizes the nucleus,
since the entire male gamete fuses with the entire female gamete to produce
and embryo? The other stuff that goes on outside this pair of fused cells
(such as the endosperm) varies from organism to organism, but it is
normally outside of the inheritance of the embryo itself. Now then, my
understanding is that there are cases of two or more male gametes fusing
with the same female nucleus. In plants this could potentially create a
viable polyploid; however, it is a nuclear thing, having nothing to do with
what is outside the nucleus, and in most organisms it usually results in
the early failure of the resulting embryo.
Perhaps this question/observation shows some ignorance on my part?
Now, I'm not sure anyone really said one male cell contributes to the
cytoplasm of the female cell and another one to the nucleus of the same
female cell. Neil seems to have responded to this idea, but I missed any
message that may have implied or stated this.
My observation would be this. If an additional male gamete "fertilized the
cytoplasm" of the female gamete that results in the embryo that produces
the next generation of plant, there would be an extra male haploid nucleus
in the cells of that embryo, and this sounds wrong. It seems it would also
play havoc on genetic expression and future reproduction, not to mention an
ever growing burden of extra male derived nuclei piling up in the cells of
the plants (unless they are "disappeared" somehow?).
I'm thinking there might be some confusion of terminology here that just
needs a bit of simple clarification.
Just another quick thought here. It is often stated that cytoplasmic DNA
comes only from the female, but my experience with biology says to me to
"never say never", because if someone says it can't happen, it almost
certainly can and does. While it would seem highly improbable, cellular
anomalies do occur, some get passed on, and it seem to me that a "sperm"
cell (male gamete) that carries a bit of cytoplasm, which might include
DNA, could exist, and perhaps could combine with a female gamete to pass on
cytoplasmic DNA from the male parent. Remember, I didn't say "does", I
said "seems like it could".
OK, I'll drop out and read the really interesting stuff from Neil and Chuck
- the real inheritance facts figures and ideas.
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