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Author Topic:   Is Human DNA as good as it gets?
Parasomnium
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Posts: 2224
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

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This message is a reply to:
 Message 1 by Mespo, posted 01-18-2006 4:35 PM Mespo has replied

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 Message 5 by Mespo, posted 01-19-2006 10:45 AM Parasomnium has not replied

  
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