Posted by: salamandercandy | February 5, 2007

How much DNA?

How much DNA do you have in your body? A DNA base pair has a length of a little less than one nanometer (a billionth of a meter). There are approximately three billion DNA base pairs in the human genome, and since we are diploid organisms, each cell actually contains six billion base pairs. Therefore, if you took all the DNA in a human cell and stretched it out, it would reach a few meters. Now, there are about 10 trillion cells in the human body. So, all the DNA in your body, if laid end to end, would reach from the Earth to the Sun a hundred times! Yes, you read that correctly. Yes, that is a long freaking way!

Now, how much DNA does a salamander have?


Let’s take the mudpuppy, Necturus maculosus. Mudpuppies are aquatic salamanders from eastern North America that retain their external gills throughout life. I’ve caught them in Cayuga Lake in upstate New York by wading through the shallows near shore at night while shining a flashlight down into the water. Mudpuppies grow to be over 40 centimeters long. These little guys have about 30 times as much DNA in every cell as a person has: about 180 billion DNA base pairs. I don’t really know how many cells a mudpuppy has, but I estimate that they weigh about a pound. Cells with large genomes tend to be larger, so so the number of cells per pound is probably less in a mudpuppy than in a human. Given their weight and cell density, let’s say that a mudpuppy has about 1/300 as many cells as an adult human. This is a very rough estimate, but it will do for our purposes. So, if you stretched out this salamander’s entire DNA library, it would also reach to the sun multiple times, but probably less than your DNA library (more like 10 times).

Let’s try another salamander example. The Japanese giant salamander, Andrias japonicus, can weigh over 100 pounds. It has about half the DNA per cell that a mudpuppy has: “only” about 90 billion DNA base pairs. But since it’s so large, and since its cells are intermediate in size between those of humans and those of mudpuppys, a giant salamander probably has nearly as many cells as an adult human. If so, the sum total of this critter’s DNA would reach from the Earth to the sun more times than your DNA would… maybe as many as 1000 times!

Why do we have so much DNA? And why do salamanders have bigger genomes than we do? After all, humans appear more complex than salamanders, so it would seem that we would need more genes… but even humans shouldn’t need genomes so large that they can be measured in astromical units. For years, biologists were puzzled by this conundrum, called the “C-value paradox.” The solution seems to be that most of the genome is junk. Both salamanders and humans have lots of DNA, but most of that DNA doesn’t actually do anything, and you could build a highly organized animal using much less DNA. Of course, this still doesn’t explain why the junk DNA exists at all. This question is not yet entirely resolved. One idea is that junk DNA is very slightly deleterious; in species with large population sizes, natural selection is able to weed out the junk, but in species with small population sizes, natural selection isn’t strong enough to stop junk from accumulating. Both salamanders and primates have relatively small effective population sizes compared to, say, most species of bacteria. Junk DNA has built up in vertebrates over millions of years, and perhaps salamanders have just ended up with more of it due to chance.

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Responses

  1. Maybe the reason Mudpuppies have so much DNA is so they’ve got thermal isozymes for activity at all temperatures between 0 and 32C.

  2. If that were true, it would be one of the most amazing cases of adaptive molecular evolution ever. My guess is that all the extra DNA is just junk, not functional genes encoding separate sets of proteins for different ranges of temperature. But we’ll never know for sure until the mudpuppy genome project comes along…

  3. I don’t think all that extra DNA is junk. Years ago nobody believed about small RNAs regulators, now they predict 10-20% genes would be regulated by this small ones; I would say 50%, most of them will come from that “junk”. Maybe mudpuppy needs more regulation for different temperatures.

  4. I think the human mind that labels something it does not understand JUNK is doomed my friend.

    In studying the universal archetypes, which over TIME reflects a human history, we witness those archetypes morphing into ARK-etypes.

    What does 95% JUNK indicate to me?
    Well the universe we inhabit is approximately 95% Dark Matter and Dark Energy combined….

    Ya know what happens to an egotistical holier than thou culture that calls the ‘secrets to life’ JUNK DNA?

    They eventually suffer the inevitable…
    95% extermination…

    Cha cha cha … here we go again …

    My ‘ground-breaking’ research indicates that in an asymmetrical UNIVERSE, filled with humans who have asymmetrical BRAINS, asymmetrical HANDS, asymmetrical HEARTS, ALL life put together by using asymmetrical HELICES indicates the following…

    JUNK DNA is connected to the unconsciousness, it is the messenger, to the invisible realm we do not ‘see’.

    The science ‘experts’ need to look into other fields, other than their own ‘specialty’ which often assists in the blinding process…

    i.e. ‘experts’ have proved we see with our brains…NOT the eyes.

    I just want to add…what is the ‘H’ particle?
    Higgs Boson is the ‘God Particle’?

    You fellas are working with such a small piece of the Pi…
    A mind that references something it does not understand JUNK, is doomed.
    IMHO

    Here is an example of where ‘archetypal’ visions takes a person…and remember the wisdom of Sir Isaac … from Sir with love…

    “About the time of the end, a body of men will be raised up, who will turn their attention to the prophecies, in the midst of much clamor and opposition.” – Sir Isaac Newton

    Have a nice fellas looking through your scopes…
    Take a step back now from the ‘scope’…take a look at the big picture.
    See how the big, macrocosm resembles the small, the microcosm?

    Sir Isaac the alchemist knew what the scientist is still learning…

    namaste

    Ra

  5. I forgot to add some required reading to the above blog, to help understand the rant more completely…

    http://kachina2012.wordpress.com/category/left-hand-pathuniversal-asymmetryright-hand-path/
    http://kachina2012.wordpress.com/about/

    The blog suggests there is a OLD way of the looking at the world…and a NEW way

    Both are valid…

    The empirical scientists are ignoring the OLD wisdom, wisdom I would like to resurrect…

    namaste

  6. And if you believe what I say is bunk junk…

    http://www.ted.com/index.php/talks/jill_bolte_taylor_s_powerful_stroke_of_insight.html
    Watch the following, it is an inspirational video of a brain anatomist who details the stroke she herself suffered….very cool insight.

    The universe as veiled is ‘asymmetrical’.
    That is the starting gate…what lay at the finish line?

    namaste

    Ra

  7. Was het maar mogelijk zoals een salamander bv een orgaan cq lichaamsdeel regenereert, dat wij dat ook zouden kunnen, maar misschien met vergelijkingsonderzoek tussen menselijk-en salamander dna…….
    Hoef je mooi niet meer naar de tandarts.

  8. Bardt,

    I don’t speak Dutch, but I think you are asking whether genetic studies on salamanders, which can regenerate body parts, could lead to similar medical therapies in humans. And intriguing possibility, and one that is being actively researched.

  9. Would it be possible like a lizard can regenerate his parts, that we could do that too as humans, maybe by comparison-research between human and-lizards dna……….

    We would not have to go to the dentist.

  10. […] https://salamandercandy.wordpress.com/2007/02/05/how-much-dna/ […]

  11. It is so surprising and amazing to know this.


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