Al wrote:
When you are looking a gene map, you are looking at a template for
making an individual that has been copied, (added to and slightly
rearranged and altered) from every individual ancestor from which it
has descended? So it seems that across species, genera and families
of organisms, the groups of genes that do something which helps the
individual pass those genes would have a common look and function
across the broad spectrum of creatures they create? These are
questions? :-)
Effectively. Turns out that although chromosomes break and swap
pieces all the time (with their partner chromosome, remember, orchids
are nominally 2N - diploid), the breakage isn't random. Geneticists
thought it was random for the longest time, but it turns out there are
'hotspots' which tend to recombine more frequently than the rest of the
chromosome. So large pieces of DNA tends to move in 'chunks'. And
yes, we have to assume (because it works, among other things), that
function and sequence are inherited from common ancestors. These
sequences change with time, but the function must be conserved if the
gene is critical. If the gene isn't critical, it can diverge faster,
but will still be related to its ancestral sequence.
Have a group of genes been found in plants that are only found in
plants which produce flowers? Have a group of genes been found in
orchids that are not found in any other flowering plants? Wouldn't
such a finding indicate that the gene group is responsible for
something that happens in flowering plants but not in other plants, or
in orchids but not in other flowering plants?
Not as far as I know. I don't think we know enough about the
genomes of enough plants. We did a project here which looked at genes
which were 'specific to plants', but not flowering vs. non-flowering.
This has holes you can drive a truck through, for various technical
reasons, btw. If there is a group of 'flowering specific genes' I don't
know about them. Doesn't mean they don't exist, and I'll be happy to
take citations...
How do they find genes? Is it possible (yet) for a trained
botanist/geneticist to look at a bunch of genes and tell if it is a
gymnosperm or an angiosperm? That identifying structure he/she is
looking for being a thing common to all angiosperms but that is not
present in gymnosperms?
Genes are found a) by similarity to known genes - we know a lot of
genes, b) by software that looks at the genome and tries to predict gene
structure - it is 'trained' on a reference set and let loose on your
genome, or c) by good old fashioned cloning - a scientist generates a
copy of a mRNA (the 'message RNA' that gets translated into a protein),
and we work backwards from there. No, we can't tell between angiosperms
and gymnosperms just by sequence. We could take a gene sequence from a
bunch of different organisms and run software that tells us what is
'most closely related' (quotes mine) to what. It might divide them into
those two classes, or not...
Did the flowering organ in plants develop in many different unrelated
species of non-flowering plants, and therefore maybe be relatively
uneasy to compare and identify in other flowering plant's genes?
I'd bet good money that flowering (as we think of it) is a single
evolutionary event, with all of the flowering plants descended from a
single common ancestor.
I am sure gene groups that do the same thing in different animals are
moved all over the place in the various species they construct and may
not even stay together on the same chromosome even if they perform the
same function, so it follows that the relatedness of species and
individuals has something to do with where known gene groups are
located in the templates when compared to each other?
I guess so... That is not a wrong way of thinking about it, anyway.
I would guess that the genes of plants would travel through time and
species the same way they travel through the genes of the animal
kingdom. A group of genes that performs a specific function in any
organism descended from a previous ancestor would be found in some
form in all species that, like the hox box gene that determines the
development of appendages in fetus. Can genes that 'make a flower' or
"make a fused reproductive organ called a column" be located by
comparing and contrasting genes from many species?
If we had enough information, probably. Somebody might be working
on it as we speak. There are a lot of questions out there. Your
questions are pretty good ones. I might steal a few for my own work, if
you don't mind... *grin*
Rob
--
Rob's Rules:
http://www.msu.edu/~halgren
1) There is always room for one more orchid
2) There is always room for two more orchids
2a. See rule 1
3) When one has insufficient credit to purchase
more orchids, obtain more credit