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Single-Celled Species' Genome As Complex As Ours?
An anonymous reader writes: "A new paper reports on the sequencing and analysis of the genome of a single-celled species known as Tetrahymena thermophila. This ciliate (like the Paramecium people look at in school) has some 27,000 genes, or nearly as many as humans. And despite existing as a single cell, this spcies encodes fantastic complexity and unusual features. For example, it has a primitive immune system that prevents the invasion of foreign DNA. Also, it is able to cordon off its germ cell lineage much as humans do with sperm and eggs. But Tetrahymena does this by having two nuclei within each cell, with one of the nuclei being held in reserve for sex. Basically, this species uses its genome complexity to function like a single celled chameleon, changing its shape and its properties in response to the changing environment. For example, when a new nutrient shows up in its neighborhood this species can build a kit to suck the nutrient in, degrade it, and turn it into cellular biomass quickly. Thus whereas humans use their genomic complexity in part to create a stable environment for the body, this species simply uses a genomic swiss army kit to make do with whatever environment it encounters."
I predict that companies will start looking at these gene sequences for application in drug development and to investigate the application of these "novel genes" in DNA repair therapies, metabolism and other applications.
I am actually pretty interested in this species from a metabolomic perspective. Organisms that can tune their physiology have a lot to teach us about the ability of metabolic networks to respond to environmental challenge or optimize their function in response to stress/disease.
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The funny thing about Origin of Species is that everyone immediately was pissed that Darwin had the nerve to say that we are descendents of monkeys.
Then a few years later, people were amazed that a simple worm has 20,000 genes. <sarcasm> How could it be that such a simple lowly creature has so many genes? Isn't more better? How could humans be beat? Blasphemy! </sarcasm>
And now it's 'news' that a single cell's genome has as many genes as a human's! When will we learn that the number of genes doesn't mean 'more advanced' or 'better off'? If this single celled organism's environment caused it to evolve more genes but physically change (seemingly) very little, why are we surprised?
My work here is dung.
Hot.
> when a new nutrient shows up in its neighborhood this species can build a kit to suck the nutrient in, degrade it,
I like where this is goin'.
> and turn it into cellular biomass quickly.
Giggity giggity goo!
I for one welcome our new single-celled overlords!
No, Mr. Green. Communism is just a red herring.
Tetrahymena are non-pathogenic free-living ciliate protozoa. They are common in fresh-water. Tetrahymena species used as model organisms in biomedical researches are T. thermophila and T. pyriformis.
http://en.wikipedia.org/wiki/Tetrahymena
Wincopy
-pentapenguin
A most of you are aware, there is a lot of "junk" DNA mixed with genes. We're begining to learn that a lot of the "junk" is another form of coded instruction. Or to force fit an analogy for the Slashdot crowd, genes code for hardware, "junk" DNA codes for software. So equating the number of genes with the complextity of an organism is only part of the picture. Not as bad as equating the number of chromosomes with complexity (corn has more than humans, I believe). But still overly simplified.
The world is made by those who show up for the job.
I always wonder why it was so hard to kill a Garden Gnome. Their single-minded genome is too complex to smash to itty bitty pieces. Maybe I need a bigger hammer...
Who said anything about sentience? We're talking about genetic complexity here, not neurological advancement. I think you have the wrong article! Ah, you didn't read it.
I always find it odd that people think our DNA would be the most complex. It's really a rather stunning conceit. Single cell organisms have had millions of years to eveolve too, why shouldn't their DNA be as rich?
Very true.
Yet again I'm reminded that evolution doesn't stop and that these "simple" organisms have had just as much selection applied to their genome as the more "complex" organisms. People think of evolution as simple bacteria turning into more complicated multicellular organisms, which then turned into more complex animals and eventually the pinnacle of evolution, people.
The reality is that evolution doesn't have a goal and that single celled life is just as rich and complex as any of the more supposedly advanced life forms.
I feel it's worth pointing out that no where in the Origin of Species does Darwin discuss human/great ape/primate evolution. I'm not even certain he used the word "evolution", but don't quote me on that. Also, no true evolutionary biologist has ever said that humans descended from monkeys. It's that whole common ancestor thing. Lot's of branches, not straight line.
Darwin himself had never heard of Mendel's theory of genetics. He proposed that offspring are a "mixture of fluids" from the mother and father.
A single post chronicling the first sexually successful slashdotter and the creation of the world's smallest slashdotter :')
EPIC! MAN! EPIC!
"this species simply uses a genomic swiss army kit to make do with whatever environment it encounters."
Give it a couple million years of natural selection and you'll get a Phoenix Foundation employee of the month.How much got screwed up by the Bible Genesis 1:27 "God created man in his own image."
Thanks to that phrase, people think humans are superior to all other forms of life. Everything else was put there for us to exploit. We don't have to live in any sort of harmony, it's all just for the consumption of us superior beings.
Don't get me wrong, I eat cows, pigs, and all that with the best of them. But I do that because I'm an omnivore, not because I'm superior to a fish.
In actuallity, survival of the fittest implies fittness for a certain environment only. To borrow someone else's analogy, you can have the best gills in the pond and you'll still die off with the rest if the pond dries up.
It's always seemed to me that there *is* an objective criterion for superiority in a species. Since we're judging superiority as fitness or the ability for a certain pattern (the genome) to continue propagating, then the superior species would be that one most able to overcome a greater variety of possible roadblocks to it's survival. To use your analogy, an amphibious fish, with watertight skin that can also breath air, would be objectively better by these criteria because it doesn't need the pond. It can live on land if need be.
In short, adaptability is what makes a species "superior". This is what has made homo sapiens the dominant large animal species on the planet - our intelligence has allowed us to adapt to damn near every (land) niche on the planet. Rats are a highly fit species for this same reason, as are cockroaches, and many fungi and microorganisms. All of these species are well-rounded and adaptable. (And by this criteria, this new species featured in TFA is likewise highly advanced). The one thing that I can see possibly giving mankind an edge up out of that group is our ability to radically change and even create environments around us, most notably including the ability to leave this planet of our own volition. (While some spores can survive in space, they couldn't just pack up and leave when the sun goes Red Giant on us all. We might be able to).
And since highly adaptable species are more fit to survive over longer periods of time, then evolutionary pressure *will* tend to select for them. And in that sense there is a sort of teleology to evolution: over time, as environments change back and forth and around to a variety of different extremes, the most flexible, adaptable, and generally well-rounded species will tend to outlive the rest. To survive in particular niches against competition from species specialized to those niches, they will have to become more capable in many areas as well; not simply jacks of all trades, but also aces of many.
You're certainly right that the old concepts of some sort of linear progression culminating in mankind are inaccurate. But that doesn't mean you have to deny any sort of progression, or any sort of objective criteria for discerning superiority or fitness between species.
-Forrest Cameranesi, Geek of all Trades
"I am Sam. Sam I am. I do not like trolls, flames, or spam."
A creationist-friendly way to segue into evolution (I've seen this done, it works in most cases):
1) Start with an explanation of what science is. At its core, science is the ongoing effort to understand our world and the universe around it, how it works, and how it came to be. Specifically, science is intended to look at the world impartially and judge it only on proveable, repeatable observations. Science is the practice of observing facts and forming opinions based solely on those facts.
2) Define a scientific theory. It's not "just a guess". A true theory is supported by all the available facts, and can be used to predict further observations. When a theory is proven wrong, it is either modified (as evolution has been many times) or thrown out entirely.
3) Explain the basics of evolution. Point out that it describes a system of nature, and not just an order of progression. The theory of evolution is not the idea that man evolved from monkeys. The idea comes from the theory, but is not an integral part of it. Evolution at its most basic level is simply stated as "life changes".
I've put it this way before: Would you agree that every generation of humanity is somehow different than the last? That with each generation, some individuals never reproduce and some are far more successful (have more kids) than others? Does that not change the gene pool for the entire species? Every generation, the gene pool changes a little bit. When those changes are cumulative, that's evolution.
4) If the subject comes up, address the fact that evolution has never been meant as a direct challenge to any faith or belief. It is simply the best model for explaining the scientific observations available. It can be contradicted tomorrow, should sufficient observations be made.
120 characters for a sig? That's bloody useless.
The human eye has a "design" error, in that the photosensitive layer is not in front, there are other cells above them. This means that the neurons that do the image processing functions in the retina must be transparent, and even so there is some absorption and scattering of light. Also, we have a blind spot in the retina where the optical nerve crosses the photosensitive layer.
In mollusks, OTOH, the outer layer of cells is the photosensitive one. The eye is more sensitive to light, has no blind spot, and allows for more data processing in the retina itself. That may be one of the reasons why octopuses are so good at camouflage, their eyes are very sensitive.
All this is one more argument for evolution and against the "intelligent design" theory.
Why the hell is this in the IT section?
All current life on Earth has been around for the exact same amount of time, i.e., since the first "cell", whatever it was. The lineage has certainly split and evolved divergently over the eons since then, but really, even "primative" organisms, if they are in existence today, have been around for the same amount of time as we humans have. In a sense, therefore, it should not be so surprising to find organisms with as much complexity as humans! It certainly is interesting to see how many commonalities there are amongst species that diverged so long ago -- clearly some convergent evolution also occured along the way -- amazing how nature finds similar solutions to common biological problems.
The objective criteria you mention must take the organism's habitat into account. You know this, I know this, but the problem is that many other people don't know this. The phrase "survival of the fittest" without the qualifier is what most people understand evolution to be, as if there were some measure of fittness that wasn't relative and subjective. This in turn leads to all sorts of misunderstandings about how evolution works, the most disturbing of which can be seen in 19th century social darwinism.
Plus, it's worth noting that not all evolutionary progress pays off. To get back to your own counterpoint about amphibious fish surviving when the pond dries up, those same fish would be a less successful species right up until the point where the water based life dies. They'd probably be a marginal species that outlives the specialists by a stroke of luck.
This is where genetic diversity matters - you never know what sort of arraingment is going to work best in the future. Often the generalists outlive the specialists, and humans are definately in the specialist category (we're completely dependant on man-made tools to survive).
As for us humans, I would argue that our environment is a technological one, and that we only consider ourselves highly evolved because we're basing our criteria on ourselves. In other words, our survival strategy is toolmaking, so we're biased in favour of that strategy over any other. I don't think it's possible to look at what we've evolved for objectively, anymore than an individual can judge themselves impartially. And it's way to easy to get into circular reasoning.
Erotic is when you use a feather. Exotic is when you use the whole chicken.
...isn't necessarily a representation of the number of actual protein products that a genome produces. Part of what makes humans so complex is the number of genes that produce multiple proteins. It isn't unique to humans, but is especially prevalent.
Beadle and Tatum's original hypothesis that "One gene encodes one enzyme" no longer holds true. Mechanisms such as alternative splicing and epigenomic effects (gene activation and silencing) can cause one gene to produce many isoforms, each which may be active differently between tissue types, and each which may have entirely different functions. Our 27,000 genes are quite possibly far more complex than another species 27,000.
It's like a microscopic MacGuyver . . .
All I have to say is: Single Cell Swiss Army Knife + Spore = Pwnage
Funny, I'm listening to Dr. Waston's 50th anniversary book of the double helix (2003) CDBook this month.
The human genome betting pool paid off at 23,299 genes in 2004, though some people suspect a few more. Most sequenced mammals appear to have about 3 billion base pairs and 25K genes. The highest animal number I heard was the puffer fish at 39K genes. The record appears the amoeba dubia at 670 billion base pairs.
Mammalian gene storage and expression is more complicated than bacteria. Dr. Watson said the typical gene is divided into eight segments (exons) with some approaching 30. Plus these may code for multiple proteins. Some biochemical stores sell DNA genes with the introns removed (cDNA). These are made from RNA templates found cells and turned back into continginuous DNA. There are about twice as many cDNAs for a mouse than there are genomes.
Yes, but most biological systems come at a price. To continue with the gills analogy, a fish with even better gills than the versatile fish could cause extiniction of the more adaptable fish. Adaptability is important, but in the short run may make no difference to other organisms that use their biological resources more directly to the current environment, its a balance of both.
To talk a bit more about humanity's being special, its in large part in the brain. I would wager that almost every other bioligical system we have is bested by others in the animal kingdom. The brain turned adaptability from hardware to software. With a brain that can reason, the long process of evoultionary selection is not so necessary for short term environmental changes. Some of the environmental changes can be compensated for be behavioral (software) changes. This gives our species orders of magnitude greater adaptability.
There is nothing in your post that a Creationist would disagree with. Define evolution as a "change in allele frequencies in a population over time" and you will find Creationists nod in agreement. Tell the creationist that natural selection plays a strong role in determining who survives, and thus the frequency of various alleles - again, you will have agreement. Commit the fallacy of equivocation, by changing the definition of evolution from above to 'all living things share a common ancestor' - and there you will get disagreement.
Creationists don't deny evolution when properly defined. They reject the Darwinist beliefs that all things share a common ancestor. When you define evolution in more than one way; demonstrate one definition as being true, then throw in another idea which goes by the same name (evolution), you are guilty of equivocation.
Many people are surprised that Creationists believe in evolution when defined as a "change in allele frequencies in a population over time". I've seen even greater surprise when I tell them that Creationists believe that natural selection takes place. This is *not* the area that they dispute. You would do well to define your own theory properly (not equivocate), and to understand that which you want to criticise.
Many people may not know this but the number of genes and amount of DNA that a particular species has does not necessarily correlate to genome complexity. Salamanders have almost 10x the amount of DNA as humans, but the amount of coding DNA is not even close to the amount of coding DNA for humans. Genetics is not that simple. It is interesting though that this organism can pick and choose which genes to express at certain times.
Absolute power corrupts absolutely. indymedia
It basically comes down to a cost/benefit analysis. If a cell/organism can benefit from a fat genome, it will. New research about "junk DNA" finds that it is not really junk, but a stored-up mass of potentially usable DNA to turn on and off as needed by essentially modifying a Goto statement(s) to skip or use them over generations. Mutations may affect where the Goto jumps to, but by packratting old genes it does not have to evolve old lessons from scratch again..
If our ancestors did not have to run from or hunt fast mean animals, then perhaps our genome would pile up with "in-case" genes also. Appearently this organism uses flexibility instead of being the leanest to survive. Humans more or less also use this strategy, but by learning with brains, not via DNA. DNA is essentially a kind of long-term brain.
Table-ized A.I.
What if on some level, our cells construct egg/sperm cells based on macroscopic-level environmental conditions?
Don't give up the day job.