Twin studies in space lead to genetic discovery

Recent studies conducted by NASA hope to improve our knowledge on the effects of human health with space travel. (Billy Brown/Flickr, Creative Commons)

As space travel becomes more and more achievable and the possibility of colonizing other astronomical bodies becomes a goal rather than a dream, one issue involving space travel still needs to be answered: What is the impact on human health? There have been relatively few scientists to travel outside of Earth’s atmosphere, and those who do are limited to relatively short journeys, typically only months at a time. The full impact of space travel on human health and physiology has yet to be completely characterized. Recent studies conducted by NASA with the help of twins hope to change this.

Twin studies, in all scientific fields, are extremely useful to researchers. Identical twins are born with same genetic code, thus any qualitative or quantitative differences observed between the two as they age can be attributed to lifestyle and environmental impacts rather than genetic underpinnings. Twins are utilized by NASA, specifically to test the genetic and psychological impact of space travel. One astronaut, Scott Kelly, was stationed on the International Space Station (ISS) for 11 months while his twin brother, Mark Kelly, remained on Earth.

Space travel impacts the body in different ways. As previously known, living in an environment with less gravity causes a decrease in bone density, muscle mass (atrophy) and total blood volume. What was more interesting, as reported by Scientific American and The Guardian, is Scott came back to Earth younger than his brother and with epigenetic differences in his chromosomes.

Deoxyribonucleic acid (DNA) serves as the genetic code for all living things. DNA, in human cells, is condensed into structures called chromosomes. At the end of each chromosome is a lot of redundant code called telomeres. Telomeres, and the degradation of them with age, have been pinpointed one of the reasons why older people seem older. When Scott came back to Earth, his telomeres were slightly longer than Mark’s. While the youthfulness gained was exceptionally minuscule, only 13 milliseconds after 11 months in space, the results ran contrary to what NASA scientists predicted while confirming what Einstein hypothesized.

The finding that was even more interesting, however, was the discovery that Scott’s DNA was more methylated, at least initially, compared to his brother’s. In eukaryote cells, methylation, or the attachment of a -CH3 molecule, prevents certain genes from being transcribed, thus deactivating the DNA. While the effects were temporary and ultimately reversed after returning to Earth, the impact of this on Scott’s general health, particularly if he stayed for longer than eleven months, is not fully understood.

Long-term effects of such epigenetic changes due to space travel, at least those found thus far, most likely have minimal effect on astronauts, at least in the current time period they spend in space. This may not hold true if the stay period is extended.

Epigenetics are a collection of modifications caused from lifestyle and environment that impact one’s DNA. One such epigenetic change is methylation which can cause either increased or decreased probability of developing physiological and psychological illnesses.

If a permanent settlement is created, say, on the Moon or Mars, inhabitants could experience profoundly different illnesses than those found on Earth with completely different likelihoods of development. Depending on the change caused by living on a distant planet, it could even be hypothesized that treatments and medicine effective on Earth may not be elsewhere.

These are all hypotheticals, but as we come closer and closer to being able to inhabit different celestial bodies, these are questions that must be answered. Already, astronauts must participate in extensive exercise programs to help combat the loss of bone and muscle density. If interplanetary living becomes a reality, such colonies may need to take preventative measures against genetic changes.

These are questions we, as a society, must be able to answer before we send humans to live on distant planets.


David Csordas is a staff columnist for The Daily Campus. He can be reached via email at david.csordas@uconn.edu.