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Author Topic:   Is Human DNA as good as it gets?
Mespo
Member (Idle past 994 days)
Posts: 158
From: Mesopotamia, Ohio, USA
Joined: 09-19-2002


Message 1 of 25 (279909)
01-18-2006 4:35 PM


Actually a two-parter if possible

I was scanning through information on ther Human Genome Project and was wondering...

1. If humans are at the top of the food chain, is our DNA as complicated as it gets? Are there any plants or animals with more complicated DNA?

2. Does human DNA contain the sum total of all the DNA that has gone before us. In other words, can human DNA be "read" as the greatest Natural Biology history text of Earthly fauna there is?

(:raig


Replies to this message:
 Message 3 by NosyNed, posted 01-19-2006 12:13 AM Mespo has not yet responded
 Message 4 by Parasomnium, posted 01-19-2006 4:13 AM Mespo has responded
 Message 6 by crashfrog, posted 01-19-2006 11:13 AM Mespo has responded
 Message 25 by Dubious Drewski, posted 03-30-2006 1:29 PM Mespo has not yet responded

    
AdminNWR
Inactive Member


Message 2 of 25 (279958)
01-19-2006 12:01 AM


Thread moved here from the Proposed New Topics forum.
  
NosyNed
Member
Posts: 8842
From: Canada
Joined: 04-04-2003
Member Rating: 7.5


Message 3 of 25 (279959)
01-19-2006 12:13 AM
Reply to: Message 1 by Mespo
01-18-2006 4:35 PM


1. If humans are at the top of the food chain, is our DNA as complicated as it gets? Are there any plants or animals with more complicated DNA?

We are not at the top of the food chain; insects and bacteria are. They eat us.

I am pretty sure (but don't know) that by some measures of complexity (number of genes, chromosomes, base pairs) we are not the most complex. It may well be that by other measure we are but I don't think that is known yet.

2. Does human DNA contain the sum total of all the DNA that has gone before us. In other words, can human DNA be "read" as the greatest Natural Biology history text of Earthly fauna there is?

Yes and no. The totality of the gene pool of all organisms is a record of all that has gone before and the enviroments they adapted to. However, the record has been written over and written over again and as you go back it is more jumbled like a palpimset (sp?) that has been used more than once.


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Parasomnium
Member (Idle past 805 days)
Posts: 2191
Joined: 07-15-2003


Message 4 of 25 (279963)
01-19-2006 4:13 AM
Reply to: Message 1 by Mespo
01-18-2006 4:35 PM


DNA: complexity and history
Mespo writes:

1. If humans are at the top of the food chain, is our DNA as complicated as it gets? Are there any plants or animals with more complicated DNA?

It depends on how you define 'complicated'. If you look at the building blocks of DNA, then the DNA of all species is equally complex, because the building blocks and the general structure of DNA units are the same for all species. But the number of these units - the length of the entire DNA molecule - and the order in which these units appear in the molecule, is different for each species. So if you define 'complicated' as the length of the DNA molecule, then some species are more 'complicated' then others.

But contrary to what you might think, this has nothing to do with our place in the food chain. For example, humans have 3 x 109 (3 billion) units in their DNA, whereas a certain amoeba (Amoeba dubia) has 67 x 1010 units. That's 223 times as 'complex' as a human. Not bad for an amoeba.

2. Does human DNA contain the sum total of all the DNA that has gone before us. In other words, can human DNA be "read" as the greatest Natural Biology history text of Earthly fauna there is?

No. Although in a certain way the history of our ancestors has been accumulating in our DNA over millions and millions of years, this accumulation is far from perfect. The accumulation is not a matter of just adding the DNA of all our ancestors together, but of copying it, editing it, and deleting some of it.

Some very basic genes, common to all life, have been carried over from generation to generation, virtually unchanged. They constitute the oldest chapters of the history book. But other genes may have been edited rigorously, making it hard to recognize them for what they once were. Their ancient history is lost forever, unless you are able to list every small change they have undergone, and in the right order too.

You must also bear in mind that a lot of the earthly fauna has developed along other branches of the evolutionary 'tree of life' than our own. From the moment their branch split from ours, their history was no longer accumulated in what was to become our DNA.

This message has been edited by Parasomnium, 19-Jan-2006 12:17 PM


"Ignorance more frequently begets confidence than does knowledge: it is those who know little, not those who know much, who so positively assert that this or that problem will never be solved by science." - Charles Darwin.

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This message is a reply to:
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Mespo
Member (Idle past 994 days)
Posts: 158
From: Mesopotamia, Ohio, USA
Joined: 09-19-2002


Message 5 of 25 (279987)
01-19-2006 10:45 AM
Reply to: Message 4 by Parasomnium
01-19-2006 4:13 AM


Re: DNA: complexity and history
But contrary to what you might think, this has nothing to do with our place in the food chain. For example, humans have 3 x 109 (3 billion) units in their DNA, whereas a certain amoeba (Amoeba dubia) has 67 x 1010 units. That's 223 times as 'complex' as a human. Not bad for an amoeba.

WOW. Great response. Obviously there is no evolutionary pressure to clean house. No "Mr. Clean Gene". I guess shutting off genes not necessary for an organism's survival is easier than dropping them off at the Salvation Army Thrift Store.

DNA obesity apparently is not an issue, either.

(:raig


This message is a reply to:
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crashfrog
Inactive Member


Message 6 of 25 (279995)
01-19-2006 11:13 AM
Reply to: Message 1 by Mespo
01-18-2006 4:35 PM


2. Does human DNA contain the sum total of all the DNA that has gone before us. In other words, can human DNA be "read" as the greatest Natural Biology history text of Earthly fauna there is?

Your cousin has a child by mating with an individual neither of you are related to.

Do you suddenly gain any portion of that individual's genes, even though you're related to their offspring? No. Neither does human DNA contain any genes except those we inherited from our ancestors and those we developed ourselves. So too have all the other species on earth developed genes that we simply don't have. Every single living organism on the planet has gone through just as much evolution as we have; in most cases, considerably more. That's a considerable amount of time for them to develop genetic sequences that have nothing to do with ours.

If humans are at the top of the food chain

There isn't really a food "chain." It's a food web, when you get right down to it. Plants use the sun and nutrients from decomposers in the soil to create sugars; animals eat the sugars; those animals are eaten by other animals, those animals die and are eaten by soil decomposers, those soil decomposers are eaten by plants and combined with energy from the sun to create sugars....

You get the idea. Humans are no more at the top of a food "chain" then they're at the top of an evolutionary "ladder", or indeed, at the top of anything. It's anthrogenic ego of the most common sort, unfortunately.


This message is a reply to:
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Replies to this message:
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Mespo
Member (Idle past 994 days)
Posts: 158
From: Mesopotamia, Ohio, USA
Joined: 09-19-2002


Message 7 of 25 (279999)
01-19-2006 11:26 AM
Reply to: Message 6 by crashfrog
01-19-2006 11:13 AM


No DNA First Edition
Every single living organism on the planet has gone through just as much evolution as we have; in most cases, considerably more. That's a considerable amount of time for them to develop genetic sequences that have nothing to do with ours.

So, if I'm understanding you crashfrog, the DNA of the most primitive organism alive today doesn't even come close to resembling the DNA of that same organism when it evolved eons ago. Combined with Parasomnium's response, there is no back-tracking to that organism's DNA First Edition?

(:raig


This message is a reply to:
 Message 6 by crashfrog, posted 01-19-2006 11:13 AM crashfrog has responded

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crashfrog
Inactive Member


Message 8 of 25 (280002)
01-19-2006 11:38 AM
Reply to: Message 7 by Mespo
01-19-2006 11:26 AM


Re: No DNA First Edition
So, if I'm understanding you crashfrog, the DNA of the most primitive organism alive today doesn't even come close to resembling the DNA of that same organism when it evolved eons ago.

I wouldn't say it doesn't come close; many genetic sequences are "conserved"; that is, they don't change much over time, or among individuals in a population.

There's clues to be had, if you know how to look. But, no rewinding the DNA to First Edition doesn't seem to be possible.

Anyway, I don't like to say "primitive." What's primitive in a contemporary context? Are bacteria "primitive", even though they're the most successful lifeform - by far - the Earth has ever known? Bacteria are adapted to their many varied environments, just as anything else is; evolution didn't stop for bacteria any more than it stopped for lizards or mammals or apes.

"Simpler" is perhaps a better term. Bacteria are definately simpler than metazoan life, like humans.


This message is a reply to:
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Replies to this message:
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mick
Member (Idle past 3095 days)
Posts: 913
Joined: 02-17-2005


Message 9 of 25 (280050)
01-19-2006 4:09 PM
Reply to: Message 5 by Mespo
01-19-2006 10:45 AM


bloated dna - population size is important
Hi Mespo

Mespo writes:

Obviously there is no evolutionary pressure to clean house

I suspect that there would be evolutionary pressure to limit the size of the genome where replication rate is highly selected. This could be the case in the gamete-producing cells of many organisms, and of course in the case of many pathogenic microorganisms.

Such organisms do seem to have more "streamlined" genomes than human beings. "Bloated" DNA (i.e. introns, repetitive elements) are found less commonly in prokaryotes than eukaryotes. Part of the reason is probably due to the strength of selection on different populations. Populations of bacteria contain huge numbers of individuals, therefore selection is stronger because genetic drift does not play such an important role in determining the frequency of stretches of useless/bloated DNA. Populations of chimpanzees, on the other hand, are relatively tiny. Selection simply isn't strong enough to overpower the drift that naturally fixes gene bloat in the genome.

in edit:
A key article for anybody interested in the evolution of genome complexity is The origins of genome complexity by Michael Lynch. You can get it free online in pdf form by doing a google search.

Here's the abstract:

quote:
Complete genomic sequences from diverse phylogenetic lineages reveal notable increases in genome complexity from prokaryotes to multicellular eukaryotes. The changes include gradual increases in gene number, resulting from the retention of duplicate genes, and more abrupt increases in the abundance of spliceosomal introns and mobile genetic elements. We argue that many of these modifications emerged passively in response to the long-term population-size reductions that accompanied increases in organism size. According to this model, much of the restructuring of eukaryotic genomes was initiated by nonadaptive processes, and this in turn provided novel substrates for the secondary evolution of phenotypic complexity by natural selection. The enormous long-term effective population sizes of prokaryotes may impose a substantial barrier to the evolution of complex genomes and morphologies.

Mick

This message has been edited by mick, 01-19-2006 04:13 PM

This message has been edited by mick, 01-19-2006 05:41 PM


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Speel-yi
Inactive Member


Message 10 of 25 (283897)
02-04-2006 1:16 PM
Reply to: Message 9 by mick
01-19-2006 4:09 PM


Re: bloated dna - population size is important
Check out C-value paradox sometime. The amount of DNA has almost no relationship to the complexity of the organism.
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Speel-yi
Inactive Member


Message 11 of 25 (284064)
02-04-2006 11:24 PM
Reply to: Message 8 by crashfrog
01-19-2006 11:38 AM


Re: No DNA First Edition
quote:
Anyway, I don't like to say "primitive." What's primitive in a contemporary context? Are bacteria "primitive", even though they're the most successful lifeform - by far - the Earth has ever known? Bacteria are adapted to their many varied environments, just as anything else is; evolution didn't stop for bacteria any more than it stopped for lizards or mammals or apes.

Primitive relates to something that comes first, as in "primary". It originally had nothing negative about it. Another way to look at the first type of anything is generalized and then things tend to move to more specialized forms, with the consequent risk of extinction that goes with specialization. You in fact can have extremely specialized bacteria, so specialized that when their host/niche dies; so do they.

At the root of the problem is how most people conceptualize evolution in that it is generally believed that species such as ourselves are at the top of the evolutionary "ladder". Only problem is...there is no ladder.

This message has been edited by Speel-yi, 02-04-2006 11:40 PM


This message is a reply to:
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crashfrog
Inactive Member


Message 12 of 25 (284085)
02-05-2006 3:11 AM
Reply to: Message 11 by Speel-yi
02-04-2006 11:24 PM


Re: No DNA First Edition
Primitive relates to something that comes first, as in "primary".

Ok, but the implied chronological relationship isn't there, either. I would hazard a guess that I'm older, by far, than almost every single living bacterium on the planet. In that sense, I'm the one who came first.

Only problem is...there is no ladder.

Oh, I see. You're agreeing with me. Ok.


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Fabric
Member (Idle past 3781 days)
Posts: 41
From: London, England
Joined: 02-27-2005


Message 13 of 25 (285349)
02-09-2006 9:47 PM


im interested......
i read the other day that our human dna has'nt changed in the last 10,000 years of recorded history, do you peeps think there will be a big sudden change or very small changes over long periods of time....

why dont we see changes in human evolution happening now...or how long do you think it will be untill we start noticing them....


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Speel-yi
Inactive Member


Message 14 of 25 (285360)
02-09-2006 10:38 PM
Reply to: Message 13 by Fabric
02-09-2006 9:47 PM


Re: im interested......
There are changes in human DNA all the time, each of us has about 10 mutations that are more or less neutral.

There are also changes in the frequency of alleles in populations over time. This in its simplest form, is evolution in the Darwinian sense.

That is to say, a population will have variation of the frequency of traits within it at any given time.

An easy way to look at it is to look at something like eye color in a population. If a community has a generation with 90 blue eyed people and 10 brown eyed people in one generation and the next has 100 blue eyed people and no brown eyed...that is evolution. The frequency of the genes has changed. (It would be safe to say that the blue eye allele has become fixed in this case.)

The above case only would involve genetic drift.

In a case involving Natural Selection, take a look at the number of people that now are carriers for Sickle Cell Anemia. The numbers are growing because of the presence of the Malaria parasite.

You also may wish to consider The Red Queen Hypothesis where a species has to continuously adapt to the selective pressures brought about by the pathogens and parasites or become extinct. (We have to keep "running" just to stay in the same place.)

The human race is constantly evolving and so are the pathogens that prey upon us. Evolution happens...


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NosyNed
Member
Posts: 8842
From: Canada
Joined: 04-04-2003
Member Rating: 7.5


Message 15 of 25 (285371)
02-09-2006 11:19 PM
Reply to: Message 13 by Fabric
02-09-2006 9:47 PM


Recent Human Evolution

i read the other day that our human dna has'nt changed in the last 10,000 years of recorded history, do you peeps think there will be a big sudden change or very small changes over long periods of time....

You'd have to supply the source for that statment. There seem to be a lot of cases where it has changed.

There is reason to think that the black death supplied enough selective pressure that europeans (and other subject to it) carry some mutations that others don't.

That is the kind of evolution that we would expect to see over the 10,000 year time frame. This sort of thing will, of course, be reduced by a much larger, interacting population.


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