Well, at least your guys are finally asking the right questions...
"A lot had to happen when eukaryotes evolved. Why aren't there any intermediate stages of this process alive today? Did all the intermediate forms go extinct, and why?" Roger asks."
Posted on 02/07/2005 1:15:22 PM PST by js1138
Giardia Bares All: Parasite genes reveal long sexual history
Christen Brownlee
While it hasn't yet been caught in the act, a single-celled parasite has been ready for sex for billions of years. A new research finding provides evidence that sexual reproduction started as soon as life forms that have nuclei and organelles within their cells branched off from their structurally simpler ancestors.
The parasite Giardia intestinalis is well known for causing a diarrheal disease that animals and people contract after drinking contaminated water. Many researchers consider this species to be one of the most ancient living members of the eukaryote, or true nucleus, lineage. However, unlike most eukaryotes, G. intestinalis and its relatives have been long considered to reproduce only asexually—by division into two identical cells.
To determine when reproduction via sperm and eggs originated, John Logsdon of the University of Iowa in Iowa City and his colleagues took a close look at G. intestinalis' mysterious reproductive life. They focused on the hallmark of sexual reproduction known as meiosis, the process that halves the number of an organism's chromosomes to make gametes such as sperm and eggs. Among available data on the G. intestinalis genome, the researchers searched for genes similar to those that control meiosis in other eukaryotes, including plants, animals, and fungi.
The researchers' analysis revealed that G. intestinalis possesses genes similar to those used for meiosis by other eukaryotes. At least 5 of those genes function only in meiosis, and 10 others have roles both in meiosis and other functions, Logsdon's team noted in the Jan. 26 Current Biology.
Although the researchers didn't establish that G. intestinalis reproduces sexually, Logsdon notes that a discreet sex life might turn up after further study. "Lack of evidence is not evidence of lack," he says.
On the other hand, the findings suggest that meiosis was established early in eukaryotic evolution, making sexual reproduction "a very central feature of being a eukaryote," says Logsdon. Bacteria and other simple-celled life forms, or prokaryotes, don't make eggs and sperm.
All living eukaryotes, including G. intestinalis, share numerous cellular features and processes that aren't seen in prokaryotes. According to Andrew Roger of Dalhousie University in Halifax, Nova Scotia, establishing that all eukaryotes are capable of meiosis could "make the evolutionary transition from prokaryote to eukaryote even more difficult to sort out.
"A lot had to happen when eukaryotes evolved. Why aren't there any intermediate stages of this process alive today? Did all the intermediate forms go extinct, and why?" Roger asks.
Logsdon says that he and his team plan to continue their research by looking for meiosis genes in other eukaryotes thought to be asexual.
References:
Ramesh, M.A., S.-B. Malik, and J.M. Logsdon Jr. 2005. A phylogenomic inventory of meiotic genes: Evidence for sex in Giardia and an early eukaryotic origin of meiosis. Current Biology 15(Jan. 26):185-191. Abstract available at
http://dx.doi.org/10.1016/j.cub.2005.01.003.
Sources:
John M. Logsdon Jr. University of Iowa Department of Biological Sciences 310 Biology Building Iowa City, IA 52242-1324
Andrew Roger Department of Biochemistry and Molecular Biology Dalhousie University Halifax, NS B3H 1X5 Canada
http://www.sciencenews.org/articles/20050129/fob1.asp
From Science News, Vol. 167, No. 5, Jan. 29, 2005, p. 67.
ping
You gonna ping gobucks?
I believe you were wondering about the subject of this article.
Is this all they have to do? LOL Like who really cares about the sexual activities of Giardia? :)
You have to wonder how Geraldo even finds time for sexual activities, the way he is always enroute from here to yonder and back.
Should I ping the list for this? We've got a lot going on already.
You could put it on the back burner for a while. I think it is important, however.
Soon ... if I'm gonna ping, I don't want it to be after 100 posts have gone by.
Maybe. It's a bit technical, which will keep your average creationist Luddite from reading it. I have a feeling this one will sink quietly.
Gives "beaver fever" a whole new meaning!
Maybe the thread will sink, but how many times does some yahoo demand to know how sex evolved.
The interesting thing is this article talks about genes that are sitting on the bench, so to speak.
You've convinced me. Now I gotta wind up the ping machine ...
Well, at least your guys are finally asking the right questions...
"A lot had to happen when eukaryotes evolved. Why aren't there any intermediate stages of this process alive today? Did all the intermediate forms go extinct, and why?" Roger asks."
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Oh my. Recessive genes in eukaryotes and prokaryotes...who woulda thunk it?!
Recessive? Sounds more like a total time-out than it does recess.
Maybe if more Giardia got invites to the prom, the sex-drive would kick in.
A couple billion years seems like an awfully long preadolescence.
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