Question

Earlier this year as part of their Twins Study, NASA issued a press release regarding preliminary results of the comparison between identical twin astronauts Scott and Mark Kelly. Scott Kelly spent a year in space (March 2015 to March 2016) aboard the International Space Station, and has spent a total of 520 days in space during his career, as opposed to a total of 54 days in space for his brother Mark. One of the ongoing investigations was the study of how space travel influences chemical changes in DNA and RNA. The researchers found that “although 93% of (Scott’s) genes’ expression returned to normal postflight, a subset of several hundred ‘space genes’ were still disrupted after return to Earth”.
(A) Many mainstream media outlets reported this incorrectly by stating that Scott Kelly's genome was now only 93% identical to his brother's. What is the difference between the correct and incorrect statements?
(B)Why do you think Scott Kelly experienced a 7% change in gene expression? (C)Of the genes with altered expression levels, what processes/pathways do you think they are involved in?

Answer 1

(A) The DNA of the two brothers was identical. Scotts DNA was 7% altered in terms of the following changes and should not be compared to his brother's but his own DNA before travelling to space.

(B) Researchers discovered that 7 percent of Scott's genes experienced long-term changes. Those genes correlate with his immune system, bone formation, DNA repair, hypoxia (deficiency in oxygen reaching tissues) and hypercapnia (excess carbon dioxide in the bloodstream).

Results from the study revealed that space travel causes an increase in methylation, the process of turning genes on and off, according to NASA. The change in gene expression caused many of the genes related to Kelly's immune system to become hyper activated and even shed mitochondrial DNA fragments into his bloodstream. Researchers aren't sure why the mitochondrial DNA freed itself from cells, but they believe it could be the body's way of coping with stress.

(C) Before the study, scientists speculated that the stress of space living would cause Scott's telomeres to shrink in comparison to his brother's. Instead, much to their surprise, the telomeres in Scott's white blood cells actually grew. Telomere are the ends of our DNA and are associated with aging. Their length decreases as the age increases. Before the study, scientists speculated that the stress of space living would cause Scott's telomeres to shrink in comparison to his brother's. Instead, much to their surprise, the telomeres in Scott's white blood cells actually grew.

Tests showed that Scott's carotid artery wall was thickened and he had increased inflammation — even immediately after landing back on Earth.

However, it's still too early to say if Scott's condition is reversible or if being in space for that long permanently has accelerated the progression of atherosclerosis — buildup of fatty deposits in arteries.

Other findings of note included a shift in the ratio of two dominant species of gut bacteria in Scott Kelly. While in space, one species dominated over the other. Back on the ground, however, the ratio returned to normal. Well this can be a subject to the freeze dried food eaten in space.

The twins both took the flu vaccine at one-year intervals, and tests show that they both had an increased cell response to the flu — meaning the vaccine was working in protecting them from contracting the flu.

Therefore, NASA concluded that the flu vaccine has the same effects in space as it does on Earth