DNA Doesn’t Look Like What You Think!
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DNA Doesn’t Look Like What You Think!


[PBS Intro] I hate to tell you this, but if you’ve ever
looked at a biology textbook, chances are it was lying to you. Or at least not telling you the whole story–
about DNA. Today, we’re going to fix that. [OPEN] Real quick, what image comes to mind when
I say “DNA”. Have you got it? You’re probably imagining something like
this, or this, or maybe this? That’s not what DNA looks like. Of course you can’t exactly take a photograph
of DNA, or see it through your typical microscope. It’s simply too small. A double helix of DNA is just 2 nanometers
wide. A DNA strand next to a piece of hair is like
a person standing next to The State of Rhode Island. Even the best light microscopes can’t see
anything much smaller than about 200 nm, because, well, light can’t really interact with something
smaller than its wavelength. This is why scientists look at super-small
things with electron microscopes, because the wavelength of an electron can be a LOT
smaller than visible light. But even *that* doesn’t give us a very good
picture of something as small as DNA. Rosalind Franklin’s famous image, that solved
the double helix structure, was made by shooting DNA with X-rays, which are also smaller than
visible light. But it isn’t really a picture of DNA, it’s
more like DNA’s shadow. *The* best we’ve done, is by basically dragging
a ridiculously small needle across the DNA and feeling the bumps, sort of like a nanometer
scale record player. Now, all these methods and others have given
us an accurate model of DNA’s double helix. But still… this isn’t really the whole
story, because that’s not how DNA looks inside our cells. Each of our cells holds 2 meters of DNA inside
a nucleus just ten millionths of a meter across… which is mind-boggling. To put that in perspective, if a double helix
were the width of a pencil line, one cell’s DNA would stretch a thousand kilometers, then
wrapped in a ball less than 5 meters wide. To fit in our cells, DNA is wrapped around
beads of protein, which are coiled again, and then again, and again… and again, until
all 2 meters of DNA in our 46 chromosomes measure less than a tenth of a millimeter
end to end. That… is efficiency. These squishy little shapes are how textbooks
usually draw chromosomes… which is also a problem, because that’s not what chromosomes
look like most of the time. DNA looks like this during a very short window
when a cell is dividing into two different cells. But when DNA is packed that tight, the cell
can’t do anything with it, like make stuff. It’s like a book that’s locked shut. Most of the time, our chromosomes are partly
unwound, in one of those medium-sized coily shapes. Now I can’t even put headphones in my pocket
without tying five knots, so you’re probably wondering how our DNA keeps from getting hopelessly
tangled. To answer that, scientists have finally figured
out how to look at a cell’s DNA in three dimensions. This is a genome in 3-D. We are so used to looking at DNA on paper,
or on a screen, we forget this stuff is floating around in three dimensions. But the nucleus isn’t just a bag full of
ramen noodles. Turns out there’s a lot more organization
than we thought. The nucleus is coated with a mesh of fibers
that give it structure, and chromosomes get anchored to this mesh. Can’t have them just floating around all
willy-nilly. Turns out each chromosome hangs out in its
own “territory” inside that web. The part of the chromosome that’s being
read and making stuff is near the center, while DNA that’s not being read is usually
closer to the edge, wound up tighter. The two copies of each of your chromosomes
aren’t even next to each other. Genes are turned on and off not just by little
flags on a string, but by how that DNA is organized in three-dimensional space. Even two bits of DNA on totally separate chromosomes
can interact in this 3-D web. How these loops and twists are arranged is
what lets cells take billions of letters of code and turn it into life. This organization is important to how cells
function normally, but it’s also a part how diseases like cancer arise, even how different
cells behave inside the brain. Simplified ways of looking at DNA are useful. They help us learn, they help us tell stories
about how these complicated machines work… but it’s important to remember that’s
not the whole story. Kind of like how the blueprints for a Saturn
V can tell you how rockets work, but they won’t tell you how to get to the moon. Now that we’ve got a better picture, we’re
able to see questions we didn’t even know to ask. Stay curious. This is for eukaryotes, things with nuclei. Bacteria pack their DNA totally differently. If you see bad DNA, tell me on twitter, and
use the hashtag #badDNA

100 thoughts on “DNA Doesn’t Look Like What You Think!

  1. I'm a biologist, and this has bothered me for years. I hope life's most interesting molecule just got a lot more interesting for you!

  2. It seemed like it was going to demonstrate an accurate visual understanding of the going ons of a nucleus, then just degenerated into another tired lay speech about important DNA is, which explains nothing, and is in no short supply. I still have no idea about the behaviour of the structure of chromosomes.

  3. Just for fun, imagine that you are that individual strand of DNA that they applied a needle too. Imagine some Giant probe coming out of no where and SCRATCHING along the surface of your epidermal layer.

  4. How do they break down dna for everyday genealogy testing when it’s just a fuzzy worm under the best electron microscope . And only one fuzzy actual photograph online . Should be millions of photographs .

  5. Lost you at 1:19 but listened to the end anyhow; often information becomes more useful as I hear more. Anyhow, thank you for your video.

  6. The title should’ve been “chromosomes don’t look like what you think”…
    smh I know I’m nitpicking but that’s what you gotta do when science isn’t explained correctly

  7. More proof the Flying Spaghetti Monster is God.

    Our pasta, who art in a colander, draining be your noodles. Thy noodle come, Thy sauce be yum, on top some grated Parmesan.

    Give us this day, our garlic bread, …and forgive us our trespasses, as we forgive those who trample on our lawns.

    Lead us not into vegetarianism, but deliver us some pizza, for thine is the meatball, the noodle, and the sauce, forever and ever.

    R’amen.

  8. Wouldn't it follow that if DNA is way smaller than the wavelength of light, and we use light to "look" at something, then DNA doesn't have a "look"; it can't be "seen". So what we can look at are models of its structure. Why is that a problem?

  9. so you say it is okay to be smart, yet you insist on insulting me by saying that DNA doesn't look like what i think! And what does "i did a science" mean anyway

  10. How is using a simplified model to explain a concept to a less informed audience a problem? Info in video is solid, but we use symbols as a base for learning more complicated topics, especially those dealing with topics that we can't even, as you mentioned, truly see in the first place. Same deal with electron orbitals: if you would have come at me as a kid with that QM fuckery I would have rage quit, and most people would have, except the extraordinarily natrurally gifted.

  11. DNA design didnt wrong in the first place, dont give false info.. thats what its look like.. u are literally saying about the bigger model, but when u zoom it (or u say not coiled) thats what DNA looks like..
    Yeah ofc its so small basically its atom/molecules bond together making stairs like model..

  12. Rosalind Franklin did not "solve" the structure of DNA. The credit was not stolen from her. She thought that Crick and Watson were barking up the wrong tree.

  13. Life is intricately complex, impossible even.

    Drs. Crick and Watson deserve to be honored as two of the greatest scientists of all time.

  14. "Not an image of DNA"
    "Well this isn't a picture, it's just a recording of the photons that bounced off something"
    Getting really tired of this clickbait. I like learning about DNA, but dear god, don't just lie to us.

  15. Get rid of the plinky background music. I know you milennials have attention spans like squirrels on Crack but the sciency guy should be entertaining enough.

  16. "Can't see it with a microscope" what the hell do you think a chromosome is if not DNA in its natural form?

  17. So much complexity and design in every living cell on Earth! Clearly the fingerprints of God are all around us!

  18. So, DNA is like a super complex code written in a book? Is it possible that a book could create itself with BILLIONS of letters of code and perfectly numbered pages from nothing and spontaneously place itself into existence? 4:02 What are the odds that the very first code of DNA just fell into place from BILLIONS and BILLIONS of letters of code and formed itself into perfect alignment from absolutely nothing, spontaneously turning itself into life? Only an all powerful and mighty Creator can do that! Psalm 139:14 – I praise you because I am fearfully and wonderfully made; your works are wonderful, I know that full well. We are all fearfully and wonderfully made..

  19. Interesting, but you didn't give us a actual image or realistic representation of an image of a strand (or segment of a strand) of DNA… so… we still don't have an accurate idea of what DNA looks like. That's like telling us what a plombus looks like by only telling us what a plombus DOESN'T look like. Not helpful. Sorry. I think in this case you did HALF a science.
    Also, if you want to correct this oversight, you could do a sequel with a realistic representation of a segment of DNA and fill us in on the way DNA transcription occurs in light of the arrangement of the DNA coiled in the Chromosomes parked against the nucleus's wall. Does the process of unzipping, transcription and ligation work from the nucleus's wall – out ? Does the unzipping, transcription and ligation, along with the coiling and coiling into the chromosomes happen in the middle of the cell nucleus and the completed ends just park themselves against the nucleus's wall opposite it's daughter chromosome in time for the cell to divide ?

  20. And yet so many out there still believe in Evolution.
    It really takes a fool to believe there is no God.

  21. if they cant see it, how do they even know its structure or even modify it or cut some part of dna? hope someone can answer my confussion

  22. So dna is kinda like transistors on a silicon chip in our computers.

    And we already have cloud computing,makes me wonder things

  23. Excuse me? How are the ball and stick or molecular models of DNA lying to us? There's nothing inconsistent between those and the much larger scale spaghetti soup model you showed us.

  24. So an intelligent mind/designer.has to be behind this..many think evolution? Lol not a chance.mind boggling? Yes thats how God rolls

  25. it's only models tho, and the prob with that seems to be that "quantum physics" nonsense is the "dominant" scientific thinking for decades in the west anyway and they son't much much: the quantum physicists

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