the human genome is fully mapped, but who’s genome is this?

Question

There are differences between everyone’s genome, so when the human genome was mapped, who were they basing it off of?

In: 99

Answer 1

The “human genome” you’re talking about is called a “reference genome” — everyone’s DNA is different, but early on we figured out that we need to have one genome that everyone can look at and make notes about: where genes are, what they do, how they differ from person to person, etc. So when we talk about “mapping the human genome”, we’re really talking about selecting a representative and then making notes about its features, locations of genes, etc.

Originally, we got DNA from blood from hundreds of donors, and randomly picked 20 from men and 20 from women to actually use. They vials of blood didn’t have the people’s names on them, so we don’t know who they were.

The idea was that we’d sequence the DNA from each person, line up the sequence from each, then decide what the most common DNA sequence was at each position, and keep track of the differences among the people. Person-to-person our DNA is *almost* identical, but not quite – everyone is a just a bit different.

In fact, some of the samples were mishandled and we weren’t able to get much sequence information out of them, meaning that most of the DNA used came from one anonymous person. While some parts a mix of DNA sequence from several people, lots of it is just based off DNA from a single person.

That was the first “Human Genome”. In the years that followed, DNA sequencing became much cheaper and faster as we improved how we do it, and designed machines to do it. What took billions of dollars and years to do at the time, can now be done in a day for a few hundred dollars.

Because it’s cheap and easy, we’ve sequenced millions of human genomes. There are teams that have done so, and made big databases that describe every tiny difference between each one they sequenced and the one that’s the reference. They’ve combined that information with the donor’s medical records so that they can use statistics to look for genes that cause diseases.