Astronaut's DNA no longer matches that of his identical twin

Audrey Hill
March 16, 2018

Because of the change, Kelly and his brother-retired astronaut Mark Kelly-are no longer considered identical twins.

Scott Kelly made news when it was revealed that the astronaut's time in space had altered his gene so much that they were now different from that of his twin brother Mark Kelly.

NASA took advantage of the unique opportunity of having a set of twin brothers as astronauts by studying each to take a closer look at the effects on the human body after spending a year in space.

NASA astronaut Scott Kelly, left, and his twin Mark get together before a press conference Friday, March 4, 2016, in Houston.

The Kelly twins are the only identical twin astronauts in history. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed. According to work done so far, Scott Kelly's time in space resulted in a lengthening in the portion of chromosomes known as telomeres. NASA believes the remaining altered may indicate longterm changes "connected to the immune system, DNA fix, bone formation networks, oxygen deprivation and elevated carbon dioxide level".

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The study was conducted by NASA's Human Research Program, and the preliminary findings were released at their Investigator's Workshop on the week of 23 January 2017. Overall, the 2018 findings corroborated those from 2017, with some additions.

They gathered the evidence after looking at "large numbers" of proteins (chains of amino acids), cytokines (substances secreted by cells in the immune system) and metabolites (substances related to metabolism) in Scott's body.

NASA described the research as a "perfect nature versus nurture study" ― one that could provide important insights into the effects of long-term spaceflight on the human body. "This is thought to be from the stresses of space travel, which can cause changes in a cell's biological pathways and ejection of DNA and RNA", researchers added. These changes can trigger the formation of new molecules or "space genes". First, there was a significant increase in average length while he was in space, and then there was a decrease in length within about 48 hours of his landing on Earth that stabilized to almost preflight levels. So they made a decision to run some tests and compare Scott's DNA to his brother's after spending some time in space, and they were pretty surprised by the results.

It relates to five biological pathways and functions, including his immune system, DNA fix, bone formation networks, hypoxia, and hypercapnia.

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