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wild to cultivated changes?
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 |
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