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Hank tells us three surprises about human DNA which we learned because of the Human Genome Project.

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Find out more about the Human Genome Project at and about the National Human Genome Research Institute at
You've heard of the Human Genome: the whole enchilada of genetic information that's encoded in our DNA.

But it's more than just genes; it's full of clues to our evolutionary history, our relationships to other animals, and... a bunch of stuff that we still haven't figured out.

The key ingredients of our DNA are four chemicals: Adenine, Thymine, Guanine, and Cytosine. These are called bases and they pair up together to form long chains of base pairs. The orders of A's, T's, C's, and G's is super important because it dictates whether an organism is a human, or a hagfish, or something else.

Back in 1990 a bunch of scientists decided that if they could figure out the exact sequence of all the base pairs, the human genome, they could cure all the diseases. 

So, they started the Human Genome Project, and researchers from over 20 countries worked for 13 years to do it, and when they were done they sat back and were like, 'E-eh, eh?'.

Because don't get me wrong; there were surprises there, but they were a little less like "Surprise!" surprises, and more like, "O-oh, didn't expect that," kind of surprises.

First, it turns out that the human genome has a lot fewer genes, that is sequences that actually code for proteins that make and do stuff, than anybody expected.
So I got my Biochemistry degree in 2002; long time ago, I recognize, but not that long ago, and my biology textbook when I was in school said that there were between eighty thousand and one hundred thousand protein-coding genes in the human genome. 

And that was wrong, really wrong; there were fewer than thirty thousand. Some less complicated animals have more than that, like a water flea has thirty-one thousand.

Second surprise, not only do we have fewer genes than we thought, but they only make up like 2 percent of our genome. The project's scientists politely referred to the rest as "non-coding" DNA, which meant they had not idea what the Watson and Crick it was for.

A third sorta-lame surprise is that sequencing our genome hasn't helped us cure cancer or anything.

Which leads geneticists to conclude that our DNA is not the only thing that calls the shots when it comes to how our bodies work.

But, the Human Genome Project has definitely changed the way that we study genetics. It's given rise to Functional and Comparative Genomics: fields that study how our genome compares to that of other species.

And this new research has lead scientists to discover that a lot of the non-coding DNA in our genome has good reasons for being there.

For instance, it turns out that a lot of our DNA came from viruses that invaded our ancestor's bodies thousands of years ago, and their genes just got stuck there, unable to evolve and unable to re-infect their hosts. Which is like weird, just, virus DNA.

Also some of our DNA contains instructions for making body parts that we don't even have anymore.

Like, our genome hasn't phased out the instructions for growing a tail. During embryonic development we no longer get the go-ahead to actually grow one, but the directions for making one are still there. 

So a lot of what we once thought was junk DNA is probably code for stuff that we just don't have anymore.

So we're living in an exciting time to study genetics and I haven't even talked about Epigenetics, which is crazy, and some new research into evolutionary developmental biology, which we did old CrashCourse episode on.

And it's all thanks in part to sequencing the human genome.

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