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What’s in a genome?

by Nick Peel | Analysis

21 May 2014

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Gone are the days of the lone biologist peering down a microscope. Research institutes across the globe are now adopting a collaborative approach when taking on the big questions in cancer.

From mathematicians to physicists, computer scientists to engineers, a new world – free from labcoats – is having a huge impact on our understanding of cancer. This approach is at the heart of how the Francis Crick Institute – Europe’s biggest and most ambitious research hub – will run and is a big part of our plans for funding new researchers in the future.

Tonight, two of our researchers who are part of that collaborative effort – Professor Nicholas Luscombe, who runs the Computational Biology group at our London Research Institute (LRI), and his colleague Dr Anna Poetsch – discuss the ins and outs of our genomes as part of this year’s Pint of Science festival.

We caught up with them for a look at what they will be covering.

What exactly is your genome?

Dr Anna Poetsch and Professor Nicholas Luscombe

Dr Anna Poetsch and Professor Nicholas Luscombe

Your genome is the biological instruction manual which makes you unique. It’s made of DNA, that iconic molecule, twisting in a double helix like a spiral ladder.

The information is stored in the ‘rungs’ of this ladder, each of which is made of a pair of four different chemicals labeled A, T, G, and C. A genome is basically a string of these letters – and it’s a very long string.

For a human, there are over three billion letters, enough to fill 120 volumes of very thick telephone books! We know all of these letters for an ‘average’ human, but we are still far from understanding it. And besides, who’s really average?

What kind of information is hidden in our genome?

Of these three billion letters, around one in 1000 differs from person to person.

Since your genome is a mixture of the blueprints from each of your parents, you can use it to work out who your parents are, and where your ancestors came from.

It can also tell you about eye colour, skin colour, facial features, and many invisible characteristics, like blood type.

How can this information advance medicine?

While the differences between people’s genomes are the reasons that some of us have blue eyes and others brown eyes, they can also tell us about our predisposition towards developing various diseases, including cancer.

For example, a simple genetic test for changes in genes called the BRCA genes can spot whether some women have a much higher risk of breast cancer than others.

Knowing this, we can screen those women more regularly to spot breast cancer early if it develops – or in some cases they may opt for a mastectomy.

But it’s not only the risk which might be different between people, but also which treatments work best. Some drugs are more effective in some patients than in others, depending on their genome.

We could use this information to adjust the combination of drugs for each individual person, offering the most suitable drug at the right time.

Why is it so difficult to ‘read’ a genome?

PintOfScienceCropAt first, it was a huge challenge to read the three billion chemical letters of the human genome.

But technology has progressed so quickly that it can now be done in two weeks, for less than £600 (or just under $1000).

The bigger problem now is that even though we can read the code, it’s so complicated that we still don’t fully understand it.

We know that three per cent of the letters form chunks of DNA that hold the recipe for proteins – these are our genes.

These proteins fulfill all kinds of specific roles around the body like haemoglobin, which transports oxygen in our blood.

But the 97 per cent of DNA which isn’t being used to store recipes for proteins is much more mysterious.

We know that some of it is used for controlling which genes are used when and where (for example, making sure that haemoglobin is only produced in the blood cells where it is needed).

And we know that switching certain genes on or off in the wrong place at the wrong time can lead to cancer. As for the rest, at the moment, we don’t know!

Why would anyone not want to read their genome?

The letters of our genome contain very personal information.

They can tell us where we come from, and our risk of disease – information that people might want to keep confidential. And, at the moment, there’s not a lot you can actually do if your genome suggests you might be at increased risk of, say, Alzheimer’s.

Today, all you can really do is make sure you have a healthy lifestyle. But do I want to know what my genome might predict?

After all, it is just a risk; it doesn’t mean I will get it for sure. Is it worth the sleepless nights? And what would my insurance company do with this information?

These are just a few of the important ethical questions that will continue to surface as we learn more about our genomes.

What does this mean for the future?

While these are challenging issues which need to be thought through, genome sequencing has huge potential in the future.

It’s now cheap and easy enough to do it almost routinely, and the benefits for medicine and health will be huge once we understand how to treat patients on a more personal basis.

Scientists around the world are working together, decoding our genetic blueprints, and working out how best to make use of these three billion letters.

Anna Poetsch and Nicholas Luscombe

Pint of Science is an international festival happening simultaneously in 21 cities in six countries. With more than 10,000 people participating this year, the LRI is very pleased to participate in the festival again.

Image credit: Genome image from Flickr