Pilgrims had nothing about eating corn in their genes either, yet they managed just fine after landing at Plymouth Rock.
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.
A variant form of a gene. If you read the page at my source, you will find a discussion of bacteria that eat nothing but Nylon. Find that in your pre-existing genes.
Pilgrims had nothing about eating corn in their genes either, yet they managed just fine after landing at Plymouth Rock.
Being personally acquainted with Mr. Giardia, I just hope he never does his reproducin' in my large intestine again!
I love it!
ROFLMAO!
Antibiotics effective against VA-resistant bacteria have been developed--unfortunately, they have really nasty side effects, like phototoxicity and hepatic necrosis. Sigh. And there are some interesting things going on with self-assembling proteins that can be used against bacteria. But i think we are a long way from another Vancomycin.
I think those nylon-eating bacteria live in my hosiery drawer.
Well, I thought that you understood the implications of and the concept of extinction.
Let's try a thought experiment/story.
You are Australopithecus. One day you are dropped on a deserted island. You find lots of food and shelter and all those good things to make life bearable.
Then one day, you see, to you horror, another ugly bipedal thing step off a raft. He's bigger and stronger, and to your way of thinking much uglier than you. You hide. He is Homo sapiens, say a Cro-Magnon.
He finds food and shelter and all the things that make life bearable.
Then one day he sees you. He says, "Hey, what's that misshapen, pipsqueak doing on my island? He's eating my coconuts", and then thinks "I wonder what he'd taste like barbequed?"
You are gone to the extinction dustbin.
Implicit in all this is the obvious (although not necessarily always true) conclusion that the first of any kind into an ecological niche, is almost always not the best suited for that niche, but since competition is not as stringent it can do well. But as soon as someting a little more refined comes along - BAM, We have a winner (and a loser, by definition).
Does this help you see the "Why"?
BTW, my personal theory (unsubstantiated, of course) is that Neanderthal disappeared because Cro-Magnon ate him. I see no evidence to disprove it, except that some may have survived in the Democrat Party.
No. Fairy tales don't answer Roger's scientific questions. Nor do oversimplifications.
Please re-read the article for this thread and take note of Roger's questions.
I might add that evolution is usually defined as a change in allele frequency caused by selection. In the seemingly unlikely event the the Great Designer gave bacteria recessive alleles for digesting Nylon, evolution still selects those and increases their frequency when needed.
A couple of things make that unlikely. We know that mutations occur. We can even force them, and we can create conditions under which they occur more frequently.
In a colony of bacteria descended from a single individual, mutation is the only possible route for change.
I like your vancomycin expose'. However, I would quibble with one point. Penicillin and all other beta-lactam antibiotics (such as cephalosporins) act by inhibiting new cell wall formation. This causes the cell to explode, since it has no osmotic protection.
I did answer it, both frivolously and seriously. Sorry you don't see it.
Just correcting an obvious typo. Moving right along!
Compared to most plastic like things nylon is easy. It is a polyamide and finding an enzyme that can cleave a polyamide is not too tough (natural amides are very common). If you like this kind of thing and have a university library close, read the papers of E.C.C. Lin on enzyme recruitment. They date back to the 60's and 70's, before the cloning rage, but they will explain in great detail the natural modification of existing enzymes to use unnatural substances as substrates.
The bugs that eat halogenated hydrocarbons are even more interesting!
So what? If the organism has no problem reproducing and nothing pressuring it to extinction, it will abide. Just because something would be preferable doesn't mean evolution will force it into existence so long as what is already the case is sufficient for the task at hand. Evolution doesn't have a structural objective independent of a functional one..
However, might I add that you just gave an excellent argument for why an intelligent designer would be expected to design differently..
The Intelligent Designer was the low bidder.
Unless evolution was the design objective, in which case it's pretty amazing stuff.
Of course they do. It's more of that "free money" that grows on trees and a 'Bush.' LOL!
Well, that is absolutely correct!
" And then lets mention: it appears as though genes not only interact with each other, but also that they have multiple functions rather than the old perception (true or not) that each gene did only one thing."
The first part of this is quite true (think of a bacterium as a very complex clock like mess of gears - anything that happens has the potential to affect any other function of the cell), however, the old perception of one gene one thing has been gone out of biology for at least 40 years. The last part of the statement is now widely accepted. It is true that some enzymes are extremely specific in their function, but many are very "loose" such as some that have both proteolytic and esterolytic activities at the same active site.
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