How to sequence the human genome - Mark J. Kiel
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0:07 - 0:09You've probably heard of the human genome,
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0:09 - 0:10the huge collection of genes
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0:10 - 0:14inside each and every one of your cells.
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0:14 - 0:14You probably also know
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0:14 - 0:17that we've sequenced the human genome,
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0:17 - 0:19but what does that actually mean?
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0:19 - 0:22How do you sequence someone's genome?
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0:22 - 0:24Let's back up a bit.
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0:24 - 0:25What is a genome?
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0:25 - 0:31Well, a genome is all the genes plus some extra
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0:31 - 0:33that make up an organism.
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0:33 - 0:35Genes are made up of DNA,
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0:35 - 0:38and DNA is made up of long, paired strands
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0:38 - 0:39of A's,
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0:39 - 0:40T's,
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0:40 - 0:42C's,
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0:42 - 0:43and G's.
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0:43 - 0:44Your genome is the code
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0:44 - 0:48that your cells use to know how to behave.
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0:48 - 0:51Cells interacting together make tissues.
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0:51 - 0:54Tissues cooperating with each other make organs.
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0:54 - 0:56Organs cooperating with each other
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0:56 - 0:58make an organism,
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0:58 - 0:59you!
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0:59 - 1:02So, you are who you are
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1:02 - 1:05in large part because of your genome.
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1:05 - 1:06The first human genome
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1:06 - 1:08was sequenced ten years ago
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1:08 - 1:10and was no easy task.
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1:10 - 1:13It took two decades to complete,
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1:13 - 1:16required the effort of hundreds of scientists
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1:16 - 1:17across dozens of countries,
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1:17 - 1:20and cost over three billion dollars.
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1:20 - 1:22But some day very soon,
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1:22 - 1:24it will be possible to know the sequence of letters
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1:24 - 1:27that make up your own personal genome
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1:27 - 1:28all in a matter of minutes
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1:28 - 1:30and for less than the cost
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1:30 - 1:32of a pretty nice birthday present.
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1:32 - 1:34How is that possible?
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1:34 - 1:36Let's take a closer look.
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1:36 - 1:39Knowing the sequence of the billions of letters
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1:39 - 1:40that make up your genome
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1:40 - 1:43is the goal of genome sequencing.
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1:43 - 1:46A genome is both really, really big
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1:46 - 1:49and very, very small.
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1:49 - 1:52The individual letters of DNA,
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1:52 - 1:55the A's, T's, G's, and C's,
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1:55 - 1:58are only eight or ten atoms wide,
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1:58 - 2:01and they're all packed together into a clump,
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2:01 - 2:03like a ball of yarn.
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2:03 - 2:05So, to get all that information
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2:05 - 2:07out of that tiny space,
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2:07 - 2:09scientists first have to break
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2:09 - 2:14the long string of DNA down into smaller pieces.
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2:14 - 2:17Each of these pieces is then separated in space
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2:17 - 2:19and sequenced individually,
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2:19 - 2:20but how?
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2:20 - 2:21It's helpful to remember
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2:21 - 2:24that DNA binds to other DNA
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2:24 - 2:28if the sequences are the exact opposite of each other.
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2:28 - 2:30A's bind to T's,
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2:30 - 2:32and T's bind to A's.
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2:32 - 2:34G's bind to C's,
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2:34 - 2:37and C's to G's.
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2:37 - 2:41If the A-T-G-C sequence of two pieces of DNA
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2:41 - 2:43are exact opposites,
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2:43 - 2:44they stick together.
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2:44 - 2:45Because the genome pieces
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2:45 - 2:47are so very small,
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2:47 - 2:49we need some way to increase
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2:49 - 2:50the signal we can detect
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2:50 - 2:53from each of the individual letters.
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2:53 - 2:54In the most common method,
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2:54 - 2:57scientists use enzymes to make thousands of copies
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2:57 - 2:59of each genome piece.
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2:59 - 3:02So, we now have thousands of replicas
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3:02 - 3:04of each of the genome pieces,
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3:04 - 3:06all with the same sequence
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3:06 - 3:10of A's, T's, G's, and C's.
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3:10 - 3:12But we have to read them all somehow.
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3:12 - 3:14To do this, we need to make
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3:14 - 3:16a batch of special letters,
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3:16 - 3:18each with a distinct color.
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3:18 - 3:21A mixture of these special colored letters and enzymes
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3:21 - 3:22are then added to the genome
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3:22 - 3:24we're trying to read.
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3:24 - 3:26At each spot on the genome,
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3:26 - 3:27one of the special letters
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3:27 - 3:29binds to its opposite letter,
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3:29 - 3:32so we now have a double-stranded piece of DNA
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3:32 - 3:35with a colorful spot at each letter.
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3:35 - 3:36Scientists then take pictures
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3:36 - 3:39of each snippet of genome.
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3:39 - 3:40Seeing the order of the colors
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3:40 - 3:44allows us to read the sequence.
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3:44 - 3:45The sequences of each
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3:45 - 3:47of these millions of pieces of DNA
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3:47 - 3:49are stitched together using computer programs
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3:49 - 3:53to create a complete sequence of the entire genome.
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3:53 - 3:54This isn't the only way
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3:54 - 3:57to read the letter sequences of pieces of DNA,
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3:57 - 3:58but it's one of the most common.
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3:58 - 4:01Of course, just reading the letters in the genome
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4:01 - 4:03doesn't tell us much.
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4:03 - 4:05It's kind of like looking through a book
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4:05 - 4:07written in a language you don't speak.
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4:07 - 4:09You can recognize all the letters
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4:09 - 4:12but still have no idea what's going on.
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4:12 - 4:14So, the next step is to decipher
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4:14 - 4:15what the sequence means,
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4:15 - 4:19how your genome and my genome are different.
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4:19 - 4:21Interpreting the genes of the genome
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4:21 - 4:23is the part scientists are still working on.
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4:23 - 4:26While not every difference is consequential,
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4:26 - 4:28the sum of these differences
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4:28 - 4:29is responsible for differences
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4:29 - 4:30in how we look,
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4:30 - 4:31what we like,
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4:31 - 4:33how we act,
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4:33 - 4:35and even how likely we are to get sick
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4:35 - 4:37or respond to specific medicines.
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4:37 - 4:39Better understanding of how disparities
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4:39 - 4:40between our genomes
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4:40 - 4:42account for these differences
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4:42 - 4:44is sure to change the way we think
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4:44 - 4:47not only about how doctors treat their patients,
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4:47 - 4:49but also how we treat each other.
- Title:
- How to sequence the human genome - Mark J. Kiel
- Description:
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View full lesson: http://ed.ted.com/lessons/how-to-sequence-the-human-genome-mark-j-kiel
Your genome, every human's genome, consists of a unique DNA sequence of A's, T's, C's and G's that tell your cells how to operate. Thanks to technological advances, scientists are now able to know the sequence of letters that makes up an individual genome relatively quickly and inexpensively. Mark J. Kiel takes an in-depth look at the science behind the sequence.
Lesson by Mark J. Kiel, animation by Marc Christoforidis.
- Video Language:
- English
- Team:
- closed TED
- Project:
- TED-Ed
- Duration:
- 05:05
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