Question: Have you found out anybody’s DNA???

Natalia Brodaczewska answered on 14 Mar 2020: last edited 14 Mar 2020 10:13 am

At the moment in most of the tests that we do for NHS patients we only look at small portions of somebody’s DNA. It means that even though we have the whole DNA in our test tube, we don’t actually ‘read’ (or as we say in science ‘sequence’) it all. It’s kind of like having a big book and only reading some sections of it to find the information that we want. We do this for several reasons. One is that even with the current technologies, it can take a very long time and cost a lot of money to sequence a whole DNA as it consists of many millions of letters (we use 4 letters to distinguish the 4 building blocks that make DNA: A, G, C and T). Another reason is that our understanding of the DNA is still quite limited – we only know what some of it means but for the most part, we only suspect what role it may have for human health but we can’t say anything for sure. So we could read out the individual letters but we couldn’t tell what they mean. Kind of like our big book is written in an new language and we only know some of the words.
One more important reason why we don’t look at the whole DNA is that it is a very personal thing – the DNA contains instructions to everything that makes up a person! So the information contained in the DNA can tell us things which other people may not want us to know or even they may not want to know themselves, like how likely they are to get some diseases or maybe reveal some information about their relatives. There are many ethical issues with knowing somebody’s DNA and this is why, at least for now, we try and only look for answers to specific questions that may help the patient and ignore the other bits.