The Human Genome Project

For let us be in no doubt about what we are witnessing today – a revolution in medical science whose implications far surpass even the discovery of antibiotics, the first great technological triumph of the 21st century…” Tony Blair

It’s the year 2000. The Human Genome Project announces that a rough draft of the human genome is complete. Sounds important, but what does it mean?

First, back to basics. Remember this?

DNA edited 2
Image source: Seaweed & Co, modified with permission

DNA. That iconic double helix, made of two DNA strands twisted together. Each strand is a string of bases that come together to form base pairs.

There are four different bases, given the letters A, T, G and C. The bases on a DNA strand are arranged into a sequence. In our cells, DNA itself is arranged in more organised structures called chromosomes.

Gene – a region of DNA that carries the information for a characteristic (eye colour, for example) that can be passed on to your children. It’s more complex than that, but we won’t go into the details.

The base sequence of genes can differ, leading to variation. These changes (known as mutations) can sometimes be damaging, and are associated with disease.

The genome of a living thing is its complete set of DNA, containing all the information needed to build it.

So, that’s the end of our genetics lesson.

aint nobody got time for that edited
Image source: Noise Blankers Radio Group via Flickr, modified with permission

If you have got time fo’ that, check out Learn Genetics.

In 1990, scientists across the world began the Human Genome Project (HGP). It had lots of goals, but the main one was to sequence the human genome –all 3 billion base pairs.

FYI: sequencing a genome means working out the order of the bases. Machines can now read the base sequence, like you reading this sentence.

…How?

In the HGP, the publicly-funded groups used hierarchical shotgun sequencing to sequence the genome.

Scientists tackle the genome in sections. A section of DNA is put into a carrier molecule called a bacterial artificial chromosome (BAC). The BAC delivers this section of our DNA to a bacterial cell, which will copy it. These DNA copies are collected, and chopped up into smaller pieces.

We put these fragments of DNA into other (smaller) carriers, that deliver the DNA to bacteria so that it can be copied and collected, like before. Finally, the base sequence is read.

Now it gets tricky. We have all these sequences, but we need to figure out what order they were in, on the chromosome they came from – we need a map.

Not your typical map, but one made up of DNA markers – short DNA sequences with a known location in the genome. Scientists can look for these markers in our DNA sequences, and use them to arrange the sequences in the correct order. Phew.

This video walks you through it:

In 2003 the HGP was declared complete, and the world went nuts. Tony Blair and Bill Clinton had been ready to party since 2000! The sequence of our genome was made freely available on the internet, so anyone could use it, and the possibilities seemed endless.

the HGP books
A print out of the human genome at the Wellcome Collection, London. Image source: Russ London via Wikipedia.

Many people thought the sequence would revolutionize medicine; allowing us to design better drugs, identify mutations linked to cancer, and more. The media was particularly interested in the potential to treat disease. If we understand which genes are associated with a disease, can we cure it?

15 years on, the picture isn’t so clear.

Research has benefited from the HGP – scientists have vast amounts of information about our genome at their fingertips, making it quicker and cheaper to explore it.

To treat disease, progress is slower. There has been progress; understanding the role of a gene in disease helps us to better understand the risk of developing that condition (which can now be explored with genetic tests). But understanding risk isn’t a cure.

Once the excitement about the HGP died down, it became clear that the next task –going from sequence to treatments – was much bigger. This takes time, and has led to some dissatisfied grumblings.

But many (although not all) scientists and journalists made it clear that the sequence was just the beginning. Figuring out what to do with it is another story entirely.

Should we believe the hype?

I find this one difficult to call. The HGP was undoubtedly a huge achievement, but talk of miracle cures and medical revolutions  were possibly too much too soon. Only time will tell…

behind the hype logo

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