Pitiful science reporting is wrong: astronaut Scott Kelly’s DNA is not 7 per cent different from that of his identical twin.
Multiple articles asserted this, although it is basically impossible, as humans share around 99.9 per cent of our DNA with each other, 98 per cent with chimpanzees – and even share around 90 per cent with house cats, and 85 per cent with mice.
The notion that Kelly’s DNA changed by 7 per cent would mean that, by living in space for a year, he’d become a pseudo-human creature so strange that it could barely be contemplated.
So where has this confusion come from?
It pretty much all comes down to the epigenome: an extra lay of control on genes that can affect their expression.
If all the DNA in a single one of your cells were to be laid out end to end, it’d be about 2 meters long. In order to fit inside each cell, it needs to be condensed. To do this, throughout its length, DNA is wrapped around small proteins called histones. As a result, it is very significantly condensed and can therefore fit inside each cell.
However, the cell needs access to the DNA in order to make new proteins, but when it’s wrapped around histones, it can’t. Therefore, evolution has gifted life with the ability to modify these histones, in order to allow either sections of DNA to be released for use, or to be condensed and shut off. This is under carefully regulated control by the cell, too.
Identical twins split from the same embryo, and so at that time share exactly the same DNA. There’s no assumption whatsoever that they have the same epigenome. The truth is that Kelly’s epigenome had changed by 7 per cent compared to his twin’s on earth.
To anyone who may think this is still a concern, there’s no reason to think it would be; your epigenome is modified by an incredibly wide host of stimuli. What you eat for breakfast can change your epigenome; sunlight on your skin; exercise or any habit of yours, pollution, or pretty much anything else you can think of can affect your genome.
Basically, your epigenome changes so that your body expresses genes in the best pattern to fit the circumstances you’re in. This does not mean your DNA changes.
Is it any surprise, then, that spending a year without gravity, with a tightly regulated diet, in a confined space might change your epigenome compared with someone who’s environment contains none of those things?
The original NASA study even made a point of saying that the epigenetic changes returned to normal once Kelly returned to Earth.
Science journalists need to take their work more seriously and write for truth – not for attention-grabbing headlines. Some of the articles surrounding this story were little more than clickbait.
Poor science journalism like this fuels misunderstanding, and contributes to myths held by some elements of the public that no amount of ‘corrections’ posted after the fact can fix.
The best way for a journalist to avoid it would be to understand what you’re reading about before you write your article. The best way for a non-scientist to know if what they’re reading is accurate or not? Check another news source – if a story seems too fantastic to be true, it’s certainly worth double checking.
Image credit: qimono via pixabay