Why do scientists want my DNA?
I came across an article on the BBC news website this week that was discussing the pressure some individuals in Iceland are under to donate samples of their DNA to the private genetic research company deCODE (http://www.bbc.co.uk/news/magazine-27903831). The UK has an equivalent charitable organisation that collects several different types of biological samples from individuals over time; the UK Biobank (links to both deCODE and UK Biobank’s webpages are at the end of this post).
So why do scientists want your DNA, and what’s so special about the Icelandic variety?
DNA (or deoxyribonucleic acid, if you want to impress your friends) acts like the instruction manual for the cells in your body, and therefore dictates how they behave, grow and function. Different cell types in your body (for example, a skin cell vs. a heart cell) ‘read’ from different ‘chapters’ of this manual, depending on what their job is (e.g. to produce skin pigment vs. rhythmically contract to make a heartbeat).
Keeping with the instruction manual metaphor …
DNA (the manual) is made up of genes (individual instructions). Every individual person has a different version of the manual, due to having slightly different versions of the instructions. The end result is ultimately the same (a human being!), but with a few variations. Some of these variations are obvious – such as hair or eye colour, height or nose shape. Other variations are less obvious, and may make a person more susceptible, or resistant to developing a particular disease or illness.
There may also be a typo in some of the instructions. Sometimes these don’t matter – the instructions can be read anyway and have the same result as if spellcheck had been completed. In other cases, the typo might change the meaning of the instructions, and the cell doesn’t quite work properly, therefore possibly causing a disease. These typos are referred to as ‘Single Nucleotide Polymorphisms’ (or SNPs).
In genetic research, the particular version of an instruction/gene you have is called a ‘Gene Variant.’
It is rarely the case that one particular gene variant causes a disease 100% of the time. It is more common that several different gene variants are ‘associated’ with a disease – that is to say that if you have one or more of those variants, you are more likely to get a particular disease. But, whether you actually do or not depends on many other things, such as your other genes and your diet & lifestyle.
But finding these ‘risk’ gene variants isn’t very straightforward.
And that’s why geneticists (gene scientists) want your DNA!!
It is now possible to scan the whole of the DNA (speed-read the manual…if you want to keep the metaphor) from an individual relatively quickly, and this method is being used to find the genetic variants that might increase the risk of disease. However, as well as these important risk gene variants, human DNA is full of useless noise! Because a particular variant won’t ‘cause’ a disease 100% of the time, huge numbers of individual’s DNA needs to be read to try and sift out the important stuff from the noise.
So this takes us back to Iceland –
Genetic ‘noise’ can come from mixtures of different ethnicities and backgrounds; different continents typically have different genetic ‘signatures,’ which account for differences in disease rates, as well as more obvious features such as appearance. With immigration and international mobility, it is difficult to find a large population of people with a very similar genetic background to each other that would reduce the genetic noise and make the risk gene variants easier to find. However, Iceland is that population, and that is what makes their DNA particularly useful for research.
So what is the point of finding risk variants if they don’t necessarily cause the disease?
Well, the eventual aim is to identify the combination of risk variants and lifestyle factors that can accurately predict whether someone will develop a particular disease. A recent high profile example of the usefulness of this knowledge is Angelina Jolie’s choice to have a mastectomy to prevent the development of breast cancer because she carried the variant of the BRCA1 gene that increases the likelihood of developing the disease. Such interventions will be more complicated for neuroscience (removing the brain isn’t really an option), but identifying important genes can also focus the research done in labs so that it can be as targeted and specific as possible to increase the chances of finding a cure.
The ultimate (and very cool) goal is to be able to accurately predict the likelihood that any individual will develop a disease based on their genes and lifestyle, and tailor a treatment to their own personal genetic makeup. Although I feel I should point out, that’s a very long way off, and there is a whole minefield of ethical issues about whether people wish to share their DNA, how it will be stored, whether people want to know if they will develop a disease or not….perhaps the subject of another post.
I encourage you to take a look at the UK Biobank website for more information and perhaps even consider getting involved in some research!