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>> Hi, I’m Adam Phillippy, a computer scientist at the
National Human Genome Research Institute. I’m one of the
scientists that helped finish the first truly complete
sequence of a human genome. Now, although I’ve worked on this
problem for years, I’m going to show you today through the
wonder of video how to do it in just seven easy steps.
Step one. Find a DNA sample. For our
project, we used a special type of cell that can multiply many
times and make lots of DNA. But you can use a more simple
sample. Blood works fine. Maybe you want to sequence yourself.
Step two. Isolate the cells by centrifugation. That’s a
scientific word for spinning something around super fast to
separate the contents. Step three. Once you have the cells
collected, you can extract the DNA and get it ready for
sequencing using some chemicals. You need to do this very
carefully so that the DNA doesn’t break into pieces. I
leave these next few steps to the experts at NIH.
When you’re done, if it looks like a glob of
snot in a test tube, you’re on the right track.
Step four. Load the snot or a sample into your
favorite sequencer. If you’re like us and just can’t decide,
use both. This one may look like some kind of space-age toaster,
but this toaster feeds DNA strands through tiny, tiny holes
called nanopores and reads the individual nucleotides as they
pass through the pores using some fancy electronics. This one
may look like a refrigerator but uses lasers and cameras to make
a movie of the DNA being copied. Pew! Pew! Now we wait for all
the data to be generated. While you are waiting, you can admire
the colorful display that shows which of the nanopores are
actively sequencing. Amazingly, you can watch the sequencing
happen in real-time. This step can take a few days.
Step six. Once we have collected all the
data, it’s time to build the genome. Unfortunately, we
haven’t figured out how to sequence a whole chromosome in
one piece yet. And instead, we’re left with millions of
smaller fragments. It’s like putting together a million-piece
puzzle. Luckily, some impatient computer scientists have written
computer programs called Genome Assemblers that can
automatically stitch everything back together again. Step seven.
Analyze the assembled DNA sequencing data for quality,
making sure there are no problems. It is good to bring in
experts for this step. People use computational tools to
search through the data like genome detectives looking for
clues and fix any gaps or errors they find. This may sometimes
look like pushing noodles around on the screen and you may love
eating noodles, but try and stay focused. You’re almost at the
finish line. That’s it. With those last few fixes, the genome
is finished. Briefly bask in the glory of knowing you sequenced a
complete human genome. If you have the informed consent of the
donor, you can now upload it to a genome database and share with
other scientists. Now, do it all over again and again and again.
With a diverse database of human genomes to compare against,
doctors will be able to better diagnose and treat diseases and
all of us will gain a better understanding of the wonderfully
big, extended family we call humanity.
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>> So great.