NASA Twins Study, “7% Of Scott DNA Is Not Matching With His Twin Brother Mark”, Is It Possible? 
NASA Twins Study, “7% Of Scott DNA Is Not Matching With His Twin Brother Mark”, Is It Possible? 

NASA Twins Study, “7% Of Scott DNA Is Not Matching With His Twin Brother Mark”, Is It Possible? 

DNA is genetic material of us made up of the three major constituents; phosphate, deoxy sugar and nitrogenous bases, present in the nucleus of a cell and therefore named as deoxyribonucleic acid.

In simple words, we can say, the DNA is a supercomputer or more than a supercomputer because it stores information in it as well as distribute it correctly to consecutive generations. 

A storage device DNA inherited genes to next-generation, further, it improves the quality of genes for the survival of an organism. 

Functionally, it encodes protein via mRNA intermediate. Different forms of proteins work differently in our body to do so many functions, hence, DNA is a very important molecule for us. 

DNA is one of the mysterious things on earth we still not know so many things about DNA even the structure of it was discovered just before 66 years ago. 

Read more on DNA, its structure, discovery, function and evidence: DNA story: The structure and function of DNA

Approximately 97% of our genome is made up of non-coding DNA that can not encode any proteins. 

The difference between the DNA composition among two individuals is just 0.1%, 99.9% of our DNA is almost the same. 

Even, only ~4% difference in genetic composition between us and chimpanzees is scientifically reported. 

Than how 7% change between two identical twins is possible!! The facts that news websites spreading are just a lie. 

In the upcoming segment of this article, we will be revealing some of the socking false details given by some respected media websites. 

But before that let’s go through, what NASA did in their twins’ study program. 

In the year 2015 NASA had decided to do a study on how the human body reacts and changes during their stay in spaceflight or at the international space station. 

The aim of the study was to see how the genetic and other factors of us changes or shifts in space, the study will establish a base for us landing on Mars in the near future. 

For doing it, NASA hired highly experienced research teams across the world who analyse different parameters of the human body. The names of the principal investigators are enlisted in the last segment of this article. 

For their ambitious project, they had selected a twin astronaut Scott Kelly and Mark Kelly. 

During the study, Mark would remain on earth while Scott would about to travel to the international space station and there he was to stay for more than a year. 

They would about to study parameters like immunome, gene expression, telomere activity, cognitive skills, biochemical, gut microbiome and epigenetics analysis. 

The main motto of the experiment was to understand “how human health is affected by extreme environments such as radiation, zero gravity (or micro-gravity) and other space factors.” 

Space is an infinite place with zero gravity, extreme radiations and loud noises and has other extreme factors we don’t know, after all, we don’t know much about the space.

For the experiment,

Mark was considered as a baseline case who was remained on earth while Scott was selected as an experimental case or test case for the present study. 

NASA Twins Study, “7% Of Scott DNA Is Not Matching With His Twin Brother Mark”, Is It Possible? 
Image credit:

The study was designed to collect data of three different intervals viz before the space flight, during the space flight and after the space flight and that data would be compared with the baseline case, Mark. 

The conclusive summary of NASA’s study is enlisted below, 

The immunological analysis reveals that the immune system responded appropriately during space travel or in the space, no significant variation was reported. 

For doing it, the researcher team conducted one simple experiment. 

They had given a flue vaccine to Scott at three different intervals: when he was on earth, when he was on a flight and when he was in space. 

The vaccine worked properly no side effect or negative impact on astronauts health was reported. 

Nutrition plays an important role for us either we are in space or on earth. The diet quality and diet quantity of astronaut’s diet plan is strictly regulated. 

Each and every ingredient selected carefully to give an astronaut a nutritious diet in space. 

Biochemical studies identified that Scott’s total body mass decreased around 7% during a stay in space, however, it would be because of the excessive exercise or controlled nutrition plan. 

The Body mass gained again within a six month after returning to eath. 

Furthermore, the folate level increased during flight as well as on a space station, again this was because of the astronaut’s strict diet plan. 

Deviation in the cognition performance was not reported either in Scott or Mark. 

Although no major changes were reported in Scott during his stay at the space station, substantial alteration in his genetic profile was reported. 

Changes in the gene expression level were detected in Scott, nevertheless, more than 90% of those changes revert back to the normal baseline in six months after returning to earth. 

Interestingly, changes in gene expression of Scott were different than Mark on earth which indicates how a body’s natural adaptation mechanism try to adapt in a different environment. 

What is gene expression?

3 billion base pairs are present in the human genome in which 3% of the portion is functional. 

Scientists have identified only 20,000 genes till now, still, almost all genes are the same in all of us but the difference is in the expression of it. 

The genses might be the same but the expression level varies from organism to organism and these factors make someone different. 

See the image below,

NASA Twins Study, “7% Of Scott DNA Is Not Matching With His Twin Brother Mark”, Is It Possible? 
The image is a hypothetical representation of keratin (KRT) gene expression in different individuals and related phenotypic changes.

Epigenetic factors such as methylation, ubiquitination, acetylation help in maintaining gene expression. 

[epcl_box type=”information”]Different genes express differently in different cells and create different tissue types. [/epcl_box]

Some other random non-pathogenic mutations were also reported in Scott that was not induced in Mark, however, scientist believed that those mutations are arisen because of radiation and other adverse conditions in space. 

One of the intriguing changes observed in Scott was the change in the length of the telomere. 

The telomere….

The telomeres are the ends of a chromosome that protect the chromosome from sticking to each other. 

Chromosomes are the complex network of DNA and proteins which helps in arranging DNA on a chromosome. 

The process called DNA packaging helps DNA to fit properly into the cell.

Structurally, the chromosome has a centromere, chromosome arms and telomeres. 

The centromere and telomeric regions are the repeated DNA sequences (called micro and mini satellite) that help in the regulation of gene expression.

The length of the telomere is directly proportional to the age of us.

After each round of replication, the length of telomere becomes shortened that decreases the overall age of an organism. 

“Shorter the telomere, shorter the age and vice verse.” 

After Scotts’ return to earth, researchers sequenced his DNA extracted from the whole blood revealed that the length of the telomere changes drastically during the flight. In Scott, an increase in telomere length was reported during his stay in space whereas telomeric changes are not reported in Mark. 

Read more on telomere and ageing: Role of Telomeres in ageing


Inflammation was reported in blood and urine samples’ of Scott which results in artery wall thicking and plaque buildup. 

The symptoms of atherosclerosis were reported due the oxidative stress and inflammation during the flight because no such signs were reported in Mark on earth. 

Now come to the original point of our story, 

The lie spread by news houses to gain readers. 

As per the articles stated on the internet, “ 7% of Scott’s DNA changed during his stay in space!

 Read what Scott say about it,

NASA Twins Study, “7% Of Scott DNA Is Not Matching With His Twin Brother Mark”, Is It Possible? 
Click here to read the tweet.

Actually, not 7% of genes but the gene expression profile of Scott changed more as compared with Mark, however, it reaches to its normal level within six months after returning to earth. 

Researches say that these changes are totally normal, our gene expression profile can change in different adverse conditions like illness, radiation, high temperature and extreme cold because after all, the main function of our genome is to keep us alive. 

Scott’s DNA is no longer matches to that of his identical twin, said by some website, and I think they got good attention and earned a lot from this article. 

But let me explained the truth, 

NASA did a twin study, but they had not revealed whether Scott and Mark are either monozygotic or dizygotic twins. 

We don’t know the fact and hence we can not say what percentage of their DNA is actually similar. 

No similar genetic profile can not exist in nature because no two individuals are the same, even the identical twins are not 100% similar to each other, throughout their life, and because of different lifestyles their genetic profile changes. 

What is monozygotic and dizygotic twins?

A twin developed from the splitting of the single zygote forms two identical embryos called monozygotic twins. 

The twins developed from two separate eggs fertilized by two different sperms called dizygotic twins or fraternal twins. 

Interesting information: 

[epcl_box type=”notice”]Identical twins do not have identical DNA profile, even their thumb fingerprints are not the same. [/epcl_box]

In different conditions, we humans or any organism accumulates so many different mutations during the entire day and the majority of them are repaired in the end, thanks to DNA repair mechanism.

As we said in the early section, even in different conditions the epigenetic profile of us changed which influence the level of gene expression. 

Hence no two individuals are genetically identical and that is also true for Scott and Mark but still, most of their DNA sequences might be same that help researchers to do a comparative analysis. 

NASA Twins Study, “7% Of Scott DNA Is Not Matching With His Twin Brother Mark”, Is It Possible? 
Original image courtesy:


As per the original NASA report, No drastic or shocking alteration was reported in Scott during his flight to space or his stay in space. 

Though his chromosome grew longer due to the telomere lengthening that might happen, because of the high folate-rich diet given during the flight (Folate profile of us is related to telomere dynamics and DNA synthesis).

Some minor biochemical, immunological and genetic changes reached to the normal range within six months after reaching to earth. 

As per NASA, the present study will help them to conduct mission Mars, their ambitious project to send humans on Mars. 

Although the study is only of its kind in the world, this data is not sufficient to conclude how the human body reacts during the long term stay in space. 

Some other information:

 NASA twin study duration: 2015- 2016

  • Scott Kelly sent off to space ar March 27, 2015, and went back to earth on March 2, 2016. 


  • Scott Kelly, NASA Astronaut, Ret.
  • Mark Kelly, NASA Astronaut, Ret. 

Principle investigators appointed for different studies: 

Telomere study: 

Principal investigator: Susan M. Bailey, Colorado state university. 

Epigenomics study: 

Principal investigator: Andy P. Feinberg, Johns Hopkins University School of Medicines. 

Biochemical study: 

Principal investigator: Scott M. Smith, NASA, JSC Nutritional Biochemistry Laboratory, KBRwyle 

Microbiome study: 

Principal investigator: Fred W. Turek, Northwestern University, Feinberg School of Medicine, Centre for Sleep and circadian Biology. 

Proteomics study: 

Principal investigator: Brinda K. Rana, University of California. 

Cognition study: 

Principal investigator: Mathias Basner, University of Pennsylvania Perelman School of Medicine. 

Gene expression study: 

Principal investigator: Christopher E. Mason, Weill Conrnell Medicine, Mason lab. 

Interactive omics: 

Principal investigator: Michael snyder, Standford School of Medicine, Genetics, Snyder lab. 


Principal investigator: Emmanuel Mignot, Stanford University. 

Click here for more detail on Twin study and researcher involved in it. 

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