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Possibilities for whole genome sequencing

In this video, Dr Michelle Bishop and Dr Steve Scott consider where we are now and how sequencing might impact us in the future.
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The human genome is really large - it’s almost 3.2 billion letters long. So, if you were to read that out one letter at a time, one every second, then that would take you about a century to read it all out. But there’s lots of information in there. One of the problems that we do have is that we don’t know what all of this information means yet. So, in a lot of cases we will get this string of letters – the As, Ts, Cs and Gs, but we don’t actually know what the function is of this information that we’re getting out.
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One of the important things about whole genome sequencing is that while we get this information, we don’t have to use all of it right now, we can select which bits we want to look at. And at the moment we’re selecting the bits that we understand. But that information is still there. We can look at it later when we start to understand a little bit more about the different aspects of the genome. We can then go back and interrogate the data again. So, I suppose we can think about it as you sequence once and you interrogate often. Although the first human genome took a long time to sequence, we’re now sequencing genomes much quicker because of changes in the technology.
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Now that we can compare lots and lots of genomes, we can get a better understanding of the differences between them, and those differences are important because they’re the ones that tell us why someone might have a particular disease or what risk they might have of certain disease. The more people’s genomes we sequence, the more that we’re understanding about the different changes and that means that we’re learning more about all the different changes, which means that we can then go back and ask the same questions again of the data. So, it’s not just a one-stop shop, we don’t just do this once. You may do the sequencing once, but the interrogation will happen possibly multiple times over a person’s lifetime.
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What’s being used in quite a lot of clinical settings is what we call whole exome sequencing. So, about 2% of our genome has what we call protein-coding genes, and these are the genes that contain the instructions for our cells to develop proteins, which is essentially what allows our cells to function and ensure that it does the job is supposed to be doing. It’s believed that quite a lot of the variations that can cause human disease, or at least these rare genetic conditions will be located in these exomes.
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So, initially it was felt that if we just sequenced these exomes we’re going to be able to find out quite a lot of this information and it means you’re only sequencing 2% of the human genome – it’s a much shorter job. The more we learn about this, the more we’re finding that people can use the technique of whole genome sequencing, sequencing all aspects of the genome, but then when you’re analysing you’re just pulling out the exomes to analyse. A lot of researchers are finding that they are getting much better results, or they’re picking up a lot more variants by using that technique rather than sequencing the exomes.
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We’ve come a long way in our understanding of genomes over the last 10-15 years. With the changes in technology we are now able to compare lots and lots of genomes and generate lots and lots of data. All of that data collectively will help us to get a much better understanding of the role of genetics and genomics in health and disease. And that will lead to much better treatments much better diagnostic methods to be able to understand how we can improve health.

In this video, Dr Michelle Bishop and Dr Steve Scott consider where we are now and what might be possible in the future. They discuss the advantages of whole genome sequencing and the contribution it could make to the advancement of medicine.

Key advantages they talk about include:

  • Whole genome sequencing provides the option to ‘sequence once, interrogate often’. Just because we have the whole genome sequence doesn’t mean that we have to look at it all now. Currently, doctors and scientists are analysing the areas of the genome that they understand, but if the whole genome sequence is already captured they can revisit other areas as we learn more without having to obtain more samples from the patient.

  • Now that advances in technology have made whole genome sequencing quicker and cheaper than ever before, we are able to sequence genomes in numbers. This means that scientists are able to compare and identify patterns in order to confidently make links between genes and disease. This will ultimately mean more specific, faster diagnosis and better treatment for patients.

  • The detailed, precise analysis that whole genome sequencing affords has resulted in surprising benefits. Scientists wanting to analyse the protein coding regions of the genome only (a process known as whole exome sequencing) have found that they have been able to obtain better results by conducting whole genome sequencing and then just analysing the protein coding region of the genome. The depth and detail of whole genome sequencing is one of its major advantages and is set to improve more in years to come.

In many ways we are still at the very beginning of the journey to understand the genome, but there is no doubt that recent advances in science and technology have been life-changing.

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This content is taken from Health Education England online course
Whole Genome Sequencing: Decoding the Language of Life and Health
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