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Author Topic: How much of our DNA is actually used?  (Read 33304 times)

Offline tweener

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How much of our DNA is actually used?
« on: 31/03/2004 05:09:37 »
I don't know too much about DNA, but I understand that while the molecule is huge, there are large sections that just repeat the same codes over and over, there are some sections that are genes but they are not expressed at all, and then there are the genes that are expressed and actually do something.  Inefficient, but what do you expect from 4 billion years of trial and error for a design.

So, my question is how much of our DNA is actually functional genes and how much is just there.  Do we really know the answer yet?

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Offline MayoFlyFarmer

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Re: How much of our DNA is actually used?
« Reply #1 on: 31/03/2004 07:05:28 »
No we don't really know the answer yet.  We've pretty much found all the genes now that we have the genome sequenced.  It came out to be about 30,000 genes (much lower than most estimates).  I don't have a percentage number for you off the top of my head as far as how much of the genome that is but its pretty small (I would guess like 2% but thats totally a guess).
Howvere that doesn't mean that thats all we use. For instance remember that how a gene is expressed depends largely on the structural conformation of the DNA/chromosome and how it is folded on itself.  While I will admit even this does not account for anywhere near the amount of non gene DNA that we have, it doesn't mean that the rest is just there.  The old term "junk DNA" has all been thrown out of the scientific vocabulary. Most scientists that i know of hypothisize that the rest of the DNA is used for something.  Remember that just because we don't know somethings function doesn't mean that it doesn't have one.

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Offline nilmot

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Re: How much of our DNA is actually used?
« Reply #2 on: 31/03/2004 08:31:28 »
We were taught that some of the repeated nonsense (not a gene) strand is unique from person to person and can be used for DNA fingerprinting.

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Offline Quantumcat

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Re: How much of our DNA is actually used?
« Reply #3 on: 31/03/2004 15:21:51 »
Read Darwin's ... (something can't remember what) by Greg Bear, it's a fantastic novel about retroviruses, it's really exciting

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Offline MayoFlyFarmer

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Re: How much of our DNA is actually used?
« Reply #4 on: 31/03/2004 20:24:59 »
yes, nilmot, you are right those ARE the parts taht are used for DNA fingerprinting, but I don't think that evolution produced those for us so that we could convieniently catch criminals.  there still ahs to be some biological function to them.

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Offline tweener

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Re: How much of our DNA is actually used?
« Reply #5 on: 01/04/2004 03:05:16 »
I never assume that because we don't know the function of something means it has no function.  And, I've never heard of "junk DNA".  I was just curious.

I read "Darwin's Children" a little while back.  It was ok, but I thought a little implausible and overdone.  I haven't read any of the other "Darwin's ..." books yet, but I probably will sometime.

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Offline MayoFlyFarmer

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Re: How much of our DNA is actually used?
« Reply #6 on: 01/04/2004 07:00:44 »
Up until not very long ago "junk DNA" was the common nomenclature, and most people paid little attenbtion to that DNA and just assumed that it served no function.

I hear so much about those "Darwin's..." books but know nothing about them.  Could someone explain to me?

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Offline christianchick

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Re: How much of our DNA is actually used?
« Reply #7 on: 01/04/2004 16:06:49 »
well, all i know is that a small difference or strand could really change alot because i do know that we and monkeys have only one difference of strand at the base of things, so it makes a BIG difference, they are real important

darwin, actually he really doesn't believe in evolution he said that there is no possisble way we could have evolved at his death bed but he also did say survival of the fittest, the weak must die

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Offline MayoFlyFarmer

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Re: How much of our DNA is actually used?
« Reply #8 on: 01/04/2004 19:29:26 »
actually in the repeat segments that tweener is referring to you can have HUGE changes in DNA sequence that often show no effect on pheno type.  But in other regions, a single base pair change can cause a drastic change in phenotype.
Darwin DID believe in evolution, he's co-credited for characterizing the theory.  Howvere you are right that before he died he said that he didn't believe that we could have came from such lower organisms that his theory predicted.  This was just because at his time so little was known about science, that it was almost impossible to comprehend something as unorthodox as humans evolving from single celled organisms.  So he did believe in evolution, just micro-scale evolutio, even though he came up with the theory that suggested macro-scale evolution.

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Offline roberth

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Re: How much of our DNA is actually used?
« Reply #9 on: 01/04/2004 23:46:52 »
and he was hedging his bets on his death bed!
 

Offline tweener

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Re: How much of our DNA is actually used?
« Reply #10 on: 05/04/2004 04:04:27 »
I've read that there are scientists that are saying the theory of evolution and natural selection is wrong. That "evolution" occurs as simply random mutations and nothing more.  A gene then becomes predominant (or not) in a species simply by the random propagation through the generations.  I don't know about it, but it sounds interesting.

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Offline MayoFlyFarmer

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Re: How much of our DNA is actually used?
« Reply #11 on: 05/04/2004 05:36:54 »
Evolution DOES come about due to random mutations in the genome of a single member of a species.  There is a chance that this gene could beat the odds and work its way to predominance within the population without neccesarily being a more adventageous trait.  Odds are strongly against this though.  
Evolution is merely a game of odds.  Saying that because a trait COULD work its way into a population without being adventageous means natural selection does not exist is like saying that just because you CAN win at roulette by betting on a single number, means you WILL every time (I'm not sure if that analogy made as much sense as I thought it would).
Remember that natural selection is NOT what causes evloution, or even what drives it, but simply what steers it in the dirrection that it goes.  And its all an odds game.  
While there are several mechanisms by which evolution comonly occurs, natural selection is an underlying factor in almost all of them.  It can also be experimentally shown quite easily.  If you want a good example of this do a google serch for "industrial melanism" possibly the best naturally designed experiment ever; it really shows natural selection at work.

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Offline chris

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Re: How much of our DNA is actually used?
« Reply #12 on: 05/04/2004 06:53:52 »
Justin

I'm not really sure where you get the idea that Darwin (the guy who first described evolution) "did not believe we could have come from such lower organisms" - he seems pretty certain on that fact in the closing conclusions of "The Origin of Species" :

"Analogy would lead me one step further, namely, to the belief that all animals and plants have descended from some one prototype...all living things have much in common, in their chemical composition, their germinal vesicles, their cellular structure, and their laws of growth and reproduction...the same poison often similarly affects plants and animals; or that the poison secreted by the gall-fly produces monstrous growths on the wild rose or oak-tree. Therefore I should infer from analogy that probably all the organic beings which have ever lived on this earth have descended from some one primordial form, into which life was first breathed..."

which you can read online here :

http://www.literature.org/authors/darwin-charles/the-origin-of-species/

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Offline ebzZzZ

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Re: How much of our DNA is actually used?
« Reply #13 on: 09/04/2004 22:45:21 »

The protein coding DNA they have decoded is about 3%
of the total ammount of DNA of the top of my head. some
say the other DNA is junk, i really don't think so. what
does the other 97% do?

any suggestions from our intellectual hosts? :)

ebzZzZ
 

Offline Ylide

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Re: How much of our DNA is actually used?
« Reply #14 on: 17/04/2004 13:46:10 »
Don't forget about mitochondrial DNA, too.  Some genes are expressed in conjunction with or solely through mDNA.

It's a comparatively small amount to what's in the nucleus, but not insignificant compare the how much of the nuclear DNA we know to be "active"

Also, females (XX chromosomal ones anyway) lose an entire chromosome's gene expression.  One of their X chromosomes supercoils and methlyates in each cell so that traits from only one X chromosome are expressed.

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Offline tweener

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Re: How much of our DNA is actually used?
« Reply #15 on: 18/04/2004 04:22:32 »
Good to see you back on the forum Jay!

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Re: How much of our DNA is actually used?
« Reply #16 on: 19/04/2004 04:25:46 »
Just to chip in Jay (and yes it's nice to see you), that you are correct, when a cell contains more than one X chromosome the additional X chromosomes are shut off, on a random basis, by a process called Lyonisation (named after the British discoverer of the phenomenon (in 1961), Mary Lyon).

The shut off, or inactivated, chromosomes form a small dense aggregation in the nucleus called a Barr Body (after Barr and Bertram, 1949).

However, not all of the genes on the Lyonised X chromosomes are shut off. Some - like XIST (which initiates the inactivation), and ZFK ((which codes for a protein involved in the production of eggs and sperm) - remain active (by an as-yet undefined mechanism). You can see this clinically in patients with conditions like Kleinfelters Syndrome in which individuals have an extra X chromosome. Phenotypically these people are male, but looking at their cells you find they have XXY - 2 X chromosomes (like a woman) plus a Y chromosome (like a male). If the extra X were completely shut off these people would be normal, but in reality they are often infertile and may show below-average intelligence.

Chris

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Offline Quantumcat

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Re: How much of our DNA is actually used?
« Reply #17 on: 31/03/2004 15:21:51 »
Read Darwin's ... (something can't remember what) by Greg Bear, it's a fantastic novel about retroviruses, it's really exciting

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Offline MayoFlyFarmer

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Re: How much of our DNA is actually used?
« Reply #18 on: 31/03/2004 20:24:59 »
yes, nilmot, you are right those ARE the parts taht are used for DNA fingerprinting, but I don't think that evolution produced those for us so that we could convieniently catch criminals.  there still ahs to be some biological function to them.

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Offline tweener

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Re: How much of our DNA is actually used?
« Reply #19 on: 01/04/2004 03:05:16 »
I never assume that because we don't know the function of something means it has no function.  And, I've never heard of "junk DNA".  I was just curious.

I read "Darwin's Children" a little while back.  It was ok, but I thought a little implausible and overdone.  I haven't read any of the other "Darwin's ..." books yet, but I probably will sometime.

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Offline MayoFlyFarmer

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Re: How much of our DNA is actually used?
« Reply #20 on: 01/04/2004 07:00:44 »
Up until not very long ago "junk DNA" was the common nomenclature, and most people paid little attenbtion to that DNA and just assumed that it served no function.

I hear so much about those "Darwin's..." books but know nothing about them.  Could someone explain to me?

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Offline christianchick

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Re: How much of our DNA is actually used?
« Reply #21 on: 01/04/2004 16:06:49 »
well, all i know is that a small difference or strand could really change alot because i do know that we and monkeys have only one difference of strand at the base of things, so it makes a BIG difference, they are real important

darwin, actually he really doesn't believe in evolution he said that there is no possisble way we could have evolved at his death bed but he also did say survival of the fittest, the weak must die

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Offline MayoFlyFarmer

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Re: How much of our DNA is actually used?
« Reply #22 on: 01/04/2004 19:29:26 »
actually in the repeat segments that tweener is referring to you can have HUGE changes in DNA sequence that often show no effect on pheno type.  But in other regions, a single base pair change can cause a drastic change in phenotype.
Darwin DID believe in evolution, he's co-credited for characterizing the theory.  Howvere you are right that before he died he said that he didn't believe that we could have came from such lower organisms that his theory predicted.  This was just because at his time so little was known about science, that it was almost impossible to comprehend something as unorthodox as humans evolving from single celled organisms.  So he did believe in evolution, just micro-scale evolutio, even though he came up with the theory that suggested macro-scale evolution.

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Offline roberth

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Re: How much of our DNA is actually used?
« Reply #23 on: 01/04/2004 23:46:52 »
and he was hedging his bets on his death bed!
 

Offline tweener

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Re: How much of our DNA is actually used?
« Reply #24 on: 05/04/2004 04:04:27 »
I've read that there are scientists that are saying the theory of evolution and natural selection is wrong. That "evolution" occurs as simply random mutations and nothing more.  A gene then becomes predominant (or not) in a species simply by the random propagation through the generations.  I don't know about it, but it sounds interesting.

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Re: How much of our DNA is actually used?
« Reply #24 on: 05/04/2004 04:04:27 »

 

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