I know a bit about this: 3. The tiny difference between life and death
Monday, June 02, 2008 | Labels: evolution, genetics, science |For the post
below this line:
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Yay, more science!
Don't like boring science stuff? Well, I could go back to wallowing, if you'd like... No? Yeah, me neither... Anyways, God, I thought this was going to be a single post. I'll be lucky if it's done in two. Maybe three? It's filling in the background that really makes it a bit much. Oh well!
---
The intro to this attempt at being a smarty-pants who knows less than he thinks is here.
Please read that first, so you can get the context of where I'm coming from.
---
(Cross-posted at the other blog)
The tiny difference between life and death
Remember the basic description:
We want... Information.
So how can small changes over time - especially if many have no noticeable effect on life and wellness - suddenly have an effect that actually matters?
Well, this actually leads into another of my pet-peeves regarding claims of evolution denialists.
In addition to the bald-faced lie that "all mutations are bad and/or lethal" (see part 1 and then part 2), another bizarre anti-evolution claim is that mutations do not "increase the information" of the DNA instruction book because mutations are just "random noise".
The use of the word "information" is the trick used by denialists in this case. It's a term the meaning of which denialists can keep changing in mid-argument so that they are always, magically, right. It's also something which no biologist would use in the way that the denialists do.
I tend to not worry about what they say, though. What they mean is very clear. They're claiming that mutations of any kind add nothing new to the world and, thus, can't fuel evolution.
Yes, it's kinda the opposite of when they say "all mutations are bad".
As with the "all mutations are bad" claim, this one is so wrong on it's face - so demonstrably false - that I have to conclude, once again, that those claiming it is true are, quite simply, lying.
To use their "information" term as *I* see fit, since they do the same, I will say this:
And I have two really good examples of this, I think.
Both examples involve relatively minor tweaks of the DNA instructions. These changes probably would have gone unnoticed by their owners under the daily grind of life, but under certain challenges thrown at them by nature, these minor differences allow the few and the lucky to survive a direct assault on their very life.
Now, there's lots of general examples of mutations conferring benefits: things that make you better at getting food, using food, using new sources of food, evading predators, catching pray, surviving hot or cold climates better, and on and on.
But I think the best initial examples are ones that are almost smack-in-the-face obvious. Ones that literally show the difference between life and death that an incredibly small, and usually un-noticed change can make.
In this post, I will turn to the first example, from the world of bacteria, the representative descendants of some of the oldest forms of life on Earth. In a subsequent post, I'll hit closer to home with a somewhat similar example from our own human DNA.
Bacteria: An Instant Mob
Bacteria are, simply, single celled creatures. That is, whereas humans are made up of trillions of individual units called "cells" - all stitched together into skin, bone, nerves, lungs, the heart, etc - every bacterium is simply a single, sometimes free floating cell.
How they make more of themselves is also different from our own method. Whereas humans use sex to make more humans, a process usually involving the massive expenditure of energy, time and (for us) money, bacteria get it over with using a simpler approach.
They just grow, and when they get close to twice their starting size, each bacterium makes a copy of its DNA instruction book. It then chops itself in half, with each new half receiving a full copy of everything.
Where there was one free-floating bacterial cell, now there is two. And then it happens again: two becomes four, four becomes eight, and so on until there is a lack of food or space, which might not happen until there's already billions of bacteria.
Bacteria are rarely seen as a single cell all on it's lonesome. Since it can create its own company - one can become two in as little as hour or, even sometimes, less - it's always a population in the making.
Each one is a snowflake, er, sort of...
If we start with the simplest situation, where a bacterial population is initially just one lone cell, a population will arise simply by cells growing and dividing over and over again.
Since we started with a single cell, this population is essentially a bunch of clones of the original.
Almost.
But, remember, as with all living things, mutations -the DNA spelling errors -always happen at some rate. And as the population of cells grows in number, reaching well into the millions or billions within hours or days, mutations occur in one cell or another pretty much all the time.
So even starting from the purity of a single cell, it doesn't take very long for there to be large numbers (in the range of millions) of tiny genetic differences from bacterial cell to bacterial cell.
Now, as pointed out in part 2, the usual rules apply:
Germ Warfare
And here is where I'll pull out an extreme life-or-death example.
While there are numerous other types of benefit that are more common, they are also more subtle in effect until seen over time. My example is blatantly apparent within almost no time at all.
So, as a wee bit of extra background... a lot of people seem to think that antibiotics, chemicals that kill different bacteria, were basically created by humans. But that's not true at all.
There has been endless mortal combat between bacteria and many of the organisms on which they sometimes prey. Many antibiotic compounds arose in such beings to fight off bacterial invasion.
In fact, bacteria even fight other bacteria - if for no other reason then for simple competition over limited resources (a concept with we humans are all too familiar). Many bacterial species have developed their own antibiotics which, while harmless to their own type, will kill bacteria of other types.
One of these antibiotics which has likely been part of inter-germ warfare for a very long time, is called streptomycin. Of course, this compound has also been used by us in modern medicine.
Streptomycin stops bacterial growth. It does this by entering into a bacterial cell and shutting down all protein production.
Specifically, the drug binds directly to a critical bit of the machinery that creates all proteins in the bacterial cell, gumming up the whole works.
The result of this is the bacteria are prevented from any further growth and replication. Essentially, bacteria are killed by streptomycin (or, more exactly, they are essentially in freeze-frame until, over time, normal degradation begins to tear away at the cells).
Some pretty extreme Natural Pressure
So, imagine a population of bacteria is minding its own business. Then, whether due to encountering the bacterial species that produce streptomycin or due to injection of the drug by a doctor, the population is suddenly pummeled with buckets of streptomycin molecules.
At this point, the environment of these bacterial cells has changed and nature (or medicine) has offered a severe challenge to the life of the population.
Waves of the drug permeate the bacteria, binding to their protein creation machinery, ultimately leading to the equivalent of organ shutdown.
The bacteria in this population are going to die.
A hidden gift
But… as I mentioned, there’s millions of cells in this population with at least one mutation somewhere in its DNA instructions. And, again, these mutations simply arose because of an occasional accident in the copying of the DNA instruction book.
Well, one of the mutations that arose was a really simple one:
A misspelling in the DNA that tells the cell how to build a part of the protein creation machinery.
It’s just a single letter misspelling so that where the DNA had once been written with the letter “A”, it now had the letter “C”.
The result of this is the type of mutation to which I referred in part 2 as a “neutral” mutation.
Remembering the analogy from that post, where cells normally had protein-making machines with an oval chain-link at a particular position, cells with this particular mutation have machines with a square-link. (Again, this is an analogy)
Now, this change ends up having no particular effect, bad or good, on the function of the protein-making machines. So cells with this mutation survived perfectly well, no harm, no foul, though they ultimately made up a tiny minority of the population.
But here’s the kicker:
That tiny change, that one spelling error, that totally harmless and permitted tweak of the protein making machine actually contains a hidden gift - one that had never been noticed by the bacteria until this time.
So while all the other cells, with the usual machinery, are slowly being destroyed, these mutants endure. They survive. And they will continue to survive – and grow and reproduce – even in this constant cloud of antibiotic attack.
And... not only that. Their survival allowed the survival of all the other mutations any of them might be carrying. Meanwhile, the rest that died took all their mutations - good, bad, or currently indifferent - with them to the grave.
The future genetic makeup of this population has now been drastically altered - in one fell swoop.
I got your information right here
This, as one of zillions of examples, puts the lie to the claim that mutations are just noise, conferring no new "information".
This one tiny change in DNA spelling conferred vast amounts of information as far as the bacteria are concerned. They didn't realize the new message they had in their midst until they encountered the right environment.
And when they did, they found that some of them indeed carried new information.
It conferred life, where there was, for all others, death.
And, on a broader level, it created a portal for all the genetic differences of the survivors to endure into the future.
To me, the ramafications for this population because of this one change are profound. The impact of this one genetic event, driven by a natural experience, will be detectable far into the future.
So, to claim that this is not "information" - using whatever shifting terms the denialists want - is simply willful ignorance of reality.
---
The next time around (when I get to it) I'll discuss a somewhat similar genetic tweak - with similar effects - that exists in humanity. Something only recently realized with rather surprising historical roots.
Yes, it's the one people keep bringing up before I can even write about it.
---
Previous posts in "I know a bit about this":
Don't like boring science stuff? Well, I could go back to wallowing, if you'd like... No? Yeah, me neither... Anyways, God, I thought this was going to be a single post. I'll be lucky if it's done in two. Maybe three? It's filling in the background that really makes it a bit much. Oh well!
---
The intro to this attempt at being a smarty-pants who knows less than he thinks is here.
Please read that first, so you can get the context of where I'm coming from.
---
(Cross-posted at the other blog)
The tiny difference between life and death
Remember the basic description:
- DNA is the instructions, written in a simple alphabet, that says how to build proteins.
- Proteins are the things that actually go about building you.
We want... Information.
So how can small changes over time - especially if many have no noticeable effect on life and wellness - suddenly have an effect that actually matters?
Well, this actually leads into another of my pet-peeves regarding claims of evolution denialists.
In addition to the bald-faced lie that "all mutations are bad and/or lethal" (see part 1 and then part 2), another bizarre anti-evolution claim is that mutations do not "increase the information" of the DNA instruction book because mutations are just "random noise".
The use of the word "information" is the trick used by denialists in this case. It's a term the meaning of which denialists can keep changing in mid-argument so that they are always, magically, right. It's also something which no biologist would use in the way that the denialists do.
I tend to not worry about what they say, though. What they mean is very clear. They're claiming that mutations of any kind add nothing new to the world and, thus, can't fuel evolution.
Yes, it's kinda the opposite of when they say "all mutations are bad".
As with the "all mutations are bad" claim, this one is so wrong on it's face - so demonstrably false - that I have to conclude, once again, that those claiming it is true are, quite simply, lying.
To use their "information" term as *I* see fit, since they do the same, I will say this:
Every single mutation ever made in DNA is a bit of new information. It is a change from the previous. Whether this information is useful, harmful, or neutral, will be seen in the fullness of time. But it is something new, nonetheless, which may end up having profound effects in ways sometimes unforeseeable.
And I have two really good examples of this, I think.
Both examples involve relatively minor tweaks of the DNA instructions. These changes probably would have gone unnoticed by their owners under the daily grind of life, but under certain challenges thrown at them by nature, these minor differences allow the few and the lucky to survive a direct assault on their very life.
Now, there's lots of general examples of mutations conferring benefits: things that make you better at getting food, using food, using new sources of food, evading predators, catching pray, surviving hot or cold climates better, and on and on.
But I think the best initial examples are ones that are almost smack-in-the-face obvious. Ones that literally show the difference between life and death that an incredibly small, and usually un-noticed change can make.
In this post, I will turn to the first example, from the world of bacteria, the representative descendants of some of the oldest forms of life on Earth. In a subsequent post, I'll hit closer to home with a somewhat similar example from our own human DNA.
Bacteria: An Instant Mob
Bacteria are, simply, single celled creatures. That is, whereas humans are made up of trillions of individual units called "cells" - all stitched together into skin, bone, nerves, lungs, the heart, etc - every bacterium is simply a single, sometimes free floating cell.
How they make more of themselves is also different from our own method. Whereas humans use sex to make more humans, a process usually involving the massive expenditure of energy, time and (for us) money, bacteria get it over with using a simpler approach.
They just grow, and when they get close to twice their starting size, each bacterium makes a copy of its DNA instruction book. It then chops itself in half, with each new half receiving a full copy of everything.
Where there was one free-floating bacterial cell, now there is two. And then it happens again: two becomes four, four becomes eight, and so on until there is a lack of food or space, which might not happen until there's already billions of bacteria.
Bacteria are rarely seen as a single cell all on it's lonesome. Since it can create its own company - one can become two in as little as hour or, even sometimes, less - it's always a population in the making.
Each one is a snowflake, er, sort of...
If we start with the simplest situation, where a bacterial population is initially just one lone cell, a population will arise simply by cells growing and dividing over and over again.
Since we started with a single cell, this population is essentially a bunch of clones of the original.
Almost.
But, remember, as with all living things, mutations -the DNA spelling errors -always happen at some rate. And as the population of cells grows in number, reaching well into the millions or billions within hours or days, mutations occur in one cell or another pretty much all the time.
So even starting from the purity of a single cell, it doesn't take very long for there to be large numbers (in the range of millions) of tiny genetic differences from bacterial cell to bacterial cell.
Now, as pointed out in part 2, the usual rules apply:
- Most mutations create no significant change in the life of any particular bacteria, either resulting in acceptable DNA spelling variations or in proteins that, though slightly different, still work the same.
- Some mutations are bad, either causing the unfortunate cell to grow slowly (pretty much a kiss of death in a population that grows and divides so fast) or by really screwing up a protein that is needed for life. In either case, these mutations rarely survive in a bacterial population.
- And then there are the few mutations that do something useful for the lucky bug.
Germ Warfare
And here is where I'll pull out an extreme life-or-death example.
While there are numerous other types of benefit that are more common, they are also more subtle in effect until seen over time. My example is blatantly apparent within almost no time at all.
So, as a wee bit of extra background... a lot of people seem to think that antibiotics, chemicals that kill different bacteria, were basically created by humans. But that's not true at all.
There has been endless mortal combat between bacteria and many of the organisms on which they sometimes prey. Many antibiotic compounds arose in such beings to fight off bacterial invasion.
In fact, bacteria even fight other bacteria - if for no other reason then for simple competition over limited resources (a concept with we humans are all too familiar). Many bacterial species have developed their own antibiotics which, while harmless to their own type, will kill bacteria of other types.
One of these antibiotics which has likely been part of inter-germ warfare for a very long time, is called streptomycin. Of course, this compound has also been used by us in modern medicine.
Streptomycin stops bacterial growth. It does this by entering into a bacterial cell and shutting down all protein production.
Specifically, the drug binds directly to a critical bit of the machinery that creates all proteins in the bacterial cell, gumming up the whole works.
The result of this is the bacteria are prevented from any further growth and replication. Essentially, bacteria are killed by streptomycin (or, more exactly, they are essentially in freeze-frame until, over time, normal degradation begins to tear away at the cells).
Some pretty extreme Natural Pressure
So, imagine a population of bacteria is minding its own business. Then, whether due to encountering the bacterial species that produce streptomycin or due to injection of the drug by a doctor, the population is suddenly pummeled with buckets of streptomycin molecules.
At this point, the environment of these bacterial cells has changed and nature (or medicine) has offered a severe challenge to the life of the population.
Waves of the drug permeate the bacteria, binding to their protein creation machinery, ultimately leading to the equivalent of organ shutdown.
The bacteria in this population are going to die.
A hidden gift
But… as I mentioned, there’s millions of cells in this population with at least one mutation somewhere in its DNA instructions. And, again, these mutations simply arose because of an occasional accident in the copying of the DNA instruction book.
Well, one of the mutations that arose was a really simple one:
A misspelling in the DNA that tells the cell how to build a part of the protein creation machinery.
It’s just a single letter misspelling so that where the DNA had once been written with the letter “A”, it now had the letter “C”.
The result of this is the type of mutation to which I referred in part 2 as a “neutral” mutation.
Remembering the analogy from that post, where cells normally had protein-making machines with an oval chain-link at a particular position, cells with this particular mutation have machines with a square-link. (Again, this is an analogy)
Now, this change ends up having no particular effect, bad or good, on the function of the protein-making machines. So cells with this mutation survived perfectly well, no harm, no foul, though they ultimately made up a tiny minority of the population.
But here’s the kicker:
That tiny change, that one spelling error, that totally harmless and permitted tweak of the protein making machine actually contains a hidden gift - one that had never been noticed by the bacteria until this time.
This mutated machinery is impervious to streptomycin.
Cells containing this mutation are resistant to streptomycin attack.
So while all the other cells, with the usual machinery, are slowly being destroyed, these mutants endure. They survive. And they will continue to survive – and grow and reproduce – even in this constant cloud of antibiotic attack.
And... not only that. Their survival allowed the survival of all the other mutations any of them might be carrying. Meanwhile, the rest that died took all their mutations - good, bad, or currently indifferent - with them to the grave.
The future genetic makeup of this population has now been drastically altered - in one fell swoop.
I got your information right here
This, as one of zillions of examples, puts the lie to the claim that mutations are just noise, conferring no new "information".
This one tiny change in DNA spelling conferred vast amounts of information as far as the bacteria are concerned. They didn't realize the new message they had in their midst until they encountered the right environment.
And when they did, they found that some of them indeed carried new information.
It conferred life, where there was, for all others, death.
And, on a broader level, it created a portal for all the genetic differences of the survivors to endure into the future.
To me, the ramafications for this population because of this one change are profound. The impact of this one genetic event, driven by a natural experience, will be detectable far into the future.
So, to claim that this is not "information" - using whatever shifting terms the denialists want - is simply willful ignorance of reality.
---
The next time around (when I get to it) I'll discuss a somewhat similar genetic tweak - with similar effects - that exists in humanity. Something only recently realized with rather surprising historical roots.
Yes, it's the one people keep bringing up before I can even write about it.
---
Previous posts in "I know a bit about this":
For the post
above this line:
I liked your depression writing better. ;)
Wow, you're frickin' smaht.