In genetics, what are the most important things we still don’t know?

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4 January
12:20
4 January
12:24

Absolutely loads. Genetics is effectively a century old. When we got to the Human Genome Project in 2001, and had a much more molecular understanding of how DNA works, it turned out that many of our preconceptions about how genetics works were not correct.

"It turned out we have way too few genes to account for our presumed sophistication. We have fewer genes than bananas, rice, water fleas or tapeworms. So that was a big surprise..."
Those things like genes for individual traits, such as eye colour – it turned out that there are almost no genes ‘for’ anything, and that we have way too few genes to account for our presumed sophistication. We have fewer genes than bananas, rice, water fleas or tapeworms. So that was a big surprise, and it meant that we had to have a really hard rethink of how human genomes work.

So now we’ve accounted for all of the genes in the human genome, which only makes up about two percent of the DNA that we have. Lots of it is scaffolding – just physical bits and pieces. Lots of it is regulatory sequences – bits that turn genes on and off, or turn the volume up and down. Lots of it is nonsense – maybe stuff that had function during our evolutionary past which is basically rusted now. And lots of it we don’t know what it does. We know it’s important, because sometimes it’s very similar in some related species, which indicates that they clearly have had a function in the past and may still have today.

"The nice thing about genetics is that because our genomes are unique, and will continue to be unique as long as we keep having babies, human variation is effectively infinite."

When we started looking for the genes, or bits of DNA, that would account for certain differences, we could only find a tiny proportion of them. Some people have cast this as a crisis, or an indication that we’ve got genetics wrong. I don’t think it is that. I think it’s a good scientific problem, in that this is all in the DNA, but we just haven’t yet got tools sophisticated enough to find the bits of DNA that account for those differences. So that’s the next ten years’ work.

Once we begin to account for those sorts of differences, we can get to the next level of understanding how DNA and genomes work. But the nice thing about genetics is that because our genomes are unique, and will continue to be unique as long as we keep having babies, human variation is effectively infinite. That’s why some people, myself included, think everyone’s genome should be sequenced at birth, to create the ultimate database of genetic variation. Only then will we be able to explain how very complex diseases, particularly psychiatric disorders, actually work.

In terms of disease genetics, which is a big driving force behind understanding fundamental genetics, one of the things we’ve been learning in the last few years is that certain types of cancer mutate at a much higher rate once they’re established. You might have an initial DNA mutation which causes a tumour in a particular tissue, and as that tumour grows, the cells within it also mutate – and that’s one of the reasons why people respond to treatment differently as the disease progresses. That’s a very important finding, because it means that hopefully, in the future, personalised treatments might be possible.

"The most progress that has been made in genomics is using ancient DNA, trying to understand the prehistory of humans."

The most progress that has been made in genomics is using ancient DNA, trying to understand the prehistory of humans – that’s a field that has been radically revolutionised in the last five years as a result of being able to sequence genomes of long-dead people. The downside is that we will probably never have very much detail of Africa, the nursery of modern humans – it’s just too hot, and DNA hasn’t survived well in Africa in the way that it has in colder climates. Africa is where we really want to know what happened a million years ago, but it looks like DNA won’t ever give those answers.

There are so many subtleties and nuances and mysteries that keep emerging the more we look. So the glib answer to the question of what remains to be learned about genetics is: almost all of it.

Adam Rutherford is geneticist, science writer and broadcaster. Author of Creation: The Origin Of Life/The Future Of Life and A Brief History of Everyone Who Ever Lived: The Stories In Our Genes.

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