Put simply, genomics is the study of genomes.
But that just begs the question, what is a genome? Why is genomics ‘special’? And what makes genomics different from genetics?
All good questions!
1. What is a genome?
At the heart of every cellular organism is a set of instructions encoded in DNA – this set of instructions is the organism’s genome. In humans, our genome is made of 23 chromosomes, which, between them, are made up of over 3 billion ‘letters’ of DNA. We inherit two sets of chromosomes, one from each of our parents, so in total we have 46 chromosomes and over 6 billion of letters of DNA.
2. Why is genomics special?
3 billion is a really BIG number! If you read out all 3 billion letters in the human genome, one letter per second, non-stop, it would take over 90 years to read out all of those letters. And that’s just reading the letters, it doesn’t take into account understanding what those letters actually do. So, it’s a real challenge to decipher an organism’s genome.
In the 1980s, a group of scientists decided it was important to decipher the human genome (although, of course, everyone’s genome is unique, with the exception of identical twins). The project to ‘sequence’ the human genome began in 1990; it took 10 years and cost $3 billion before the first draft of the human genome was completed.
Now, we can sequence a human genome in a few days for a few thousand dollars – that is a staggering rate of progress.
This ability, to examine whole genomes, rather than discrete sections of DNA (such as individual genes) is still relatively new, but it is fast becoming one of, if not the most, important way of studying all areas of biology, not just human health.
3. Why is genomics different to genetics?
Genomics and genetics are very much on a continuum – they are both concerned with DNA, how it is inherited and how it works. Traditionally, genetics tends to focus on small elements of DNA (like genes), whereas genomics tends to focus on all of a genome, not just parts of it. But it’s still very difficult to draw a neat line between genetics and genomics – genetics doesn’t always focus on single genes and genomics doesn’t always focus on an organism’s entire DNA sequence!
Genetics can be thought of as fishing with a rod, while genomics is more akin to fishing with a net, or trawling!
In terms of human health, genomics lets researchers tease out the connection between small changes in DNA that might occur anywhere in a genome and a particular human condition. Importantly, where possible, genomics also tries to consider environmental factors and the relationship between the environment and its affect on the genome. For example, smoking causes a large number of changes across many different genes, which often results in cancer.
This new focus on the sequence of DNA rather than how DNA is inherited (‘sequence’ versus ‘transmission’ genetics) is likely to be a step change that underpins much future research.