Cytogenetic Effects of Ionizing Radiation in Peripheral Lymphocytes of ISS Crewmembers (Chromosome-2) - 11.22.16

Overview | Description | Applications | Operations | Results | Publications | Imagery

ISS Science for Everyone

Science Objectives for Everyone
Chromosome-2, a European Space Agency experiment, is a continuation of the Chromosome investigation performed on earlier ISS expeditions. White blood cells (lymphocytes) are collected from crewmembers preflight and postflight. The lymphocytes are examined using different analytic methods to determine quantity and quality of genetic changes resulting from exposure to cosmic radiation, particularly ionizing radiation.
Science Results for Everyone
The Chromosome-2 study determined that current astronaut radiation exposure fall well below the NASA limit, with galactic cosmic rays responsible for 80 percent or more of dose absorbed aboard the station. Early studies indicate that radiation during long-duration flights can increase chromosome damage, whereas shorter missions do not. Samples collected within a week or two of space flight provide reliable estimates of radiation dose and risk, but retrospective doses may be difficult to estimate because chromosomal damages disappear over time. Estimates from individuals on repeated or very long missions also may be complicated by an adaptive response to space radiation.

The following content was provided by Christian Johannes, Ph.D., and is maintained in a database by the ISS Program Science Office.
Information provided courtesy of the Erasmus Experiment Archive.
Experiment Details


Principal Investigator(s)
Christian Johannes, Ph.D., University of Duisburg, Essen, Essen, Germany

Alexandra Antonopoulos, University of Duisburg, Essen, Essen, Germany
Wolfgang Goedecke, Ph.D., University of Duisburg, Essen, Essen, Germany
Markus Horstmann, Ph.D., University of Duisburg, Essen, Essen, Germany

European Space Agency (ESA), Noordwijk, Netherlands

Sponsoring Space Agency
European Space Agency (ESA)

Sponsoring Organization
Information Pending

Research Benefits
Information Pending

ISS Expedition Duration
October 2005 - April 2008

Expeditions Assigned

Previous Missions
Earlier versions of this experiment flew on the Space Shuttle and the Russian Space Station, Mir, as well as, ISS Expeditions 6-11.

^ back to top

Experiment Description

Research Overview

  • This study will assess changes in the morphology of chromosomes, particularly chromosomal aberrations by taking into account the sensitivity to radiation by each crew member. The frequency and the type of chromosomal aberrations depend on characteristics and doses of ionizing radiation the crewmembers are exposed to while in orbit.

  • Chromosomes collected from blood lymphocytes are scored for different types of abnormalities before and after a stay on ISS. Some of the analysis methods are new, and will provide a new way of visualizing all changes, particularly those increasing the risk of cancer.

Cosmic radiation is a major risk factor in manned space missions. This investigation will give a better insight into the mutagenic burden of astronauts during space flights as consequence of exposure to the complex cosmic radiation field. Although it can be assumed that radiation plays a major role in mutation induction in astronauts, synergistic influences such as weightlessness, acceleration, vibration hyperthermia, noise microwave radiation, physical exercises, trauma, and infections cannot be ruled out.

During flights astronauts are chronically exposed to radiations of solar and galactic origin. The space radiation field consists of electrons, protons, heavy particles, and secondary radiation like bremsstrahlung, neutrons, and charged particles created by interactions of primary radiations with nuclei of spacecraft shielding material or the human body (Reitz et al., 1996). The contribution of the dose of single radiation types depends on altitude and inclination of the spacecraft, effective shielding thickness and solar activity during the mission.

^ back to top


Space Applications
Information Pending

Earth Applications
Information Pending

^ back to top


Operational Requirements and Protocols
The Chromosome-2 experiment will use astronauts as test subjects, but no actual in-flight experiment or data collection will be carried out. To assess the genetic impact of space radiation, blood (15 mL) is drawn before and directly after flights by venous puncture. Whole blood cultures will be set up with phytohemagglutinin to stimulate lymphocytes to undergo mitoses. After 48 h mitotic cells will be arrested with Colcemid, fixed and prepared on slides for microscopic analysis. The preparations will be scored for chromosomal aberrations. Three different staining procedures shall be performed to assess all types of aberrations induced by ionising radiations:

  • classical Giemsa block-staining to score dicentric and ring chromosomes

  • multicolor fluorescence in-situ hybridisation to score reciprocal translocations and insertions

  • multicolor banding fluorescence in-situ hybridisation of a selected chromosome pair to score for inversions and translocations between homologous chromosomes.
A quantitative comparison between pre- and postflight aberration values will give information about chromosome breaking effects of cosmic radiation in blood lymphocytes of astronauts. Information will be generated about the participation of each chromosome pair on aberration formation as well as the inter- and intrachromosomal distribution of different aberration types.

The association of chromosomal aberrations with an enhanced cancer risk stresses the importance of the planned research. The data obtained will be helpful in order to carefully plan space flight missions.

^ back to top

Decadal Survey Recommendations

Information Pending

^ back to top

Results/More Information

As astronauts spend longer periods in space, it has become more important to accurately measure radiation doses and assess individual risk for long-duration space flights. Chromosome damage in peripheral blood lymphocytes, a type of white blood cell (WBC), is commonly used as an indicator of radiation exposure, and the introduction of the fluorescence in situ hybridization (FISH) chromosome painting technique has made it possible to "paint" individual chromosomes with different colors so alterations can be identified as multi-color chromosomes allowing for more detailed and accurate analysis.

NASA has implemented a radiation biodosimetry program that utilizes FISH to determine chromosomal damage in US astronauts who participate in long-duration missions. All crewmembers returning from ISS missions are evaluated for chromosomal damage in lymphocyte cells with this technique. For this study, physical and biological doses for 23 ISS astronauts yielded average effective doses and individual or population-based biological doses for the approximately 6-month missions of 85 or 81 mGy-Eq (milligray-equivalent), respectively, which is well below NASA limit of 250 mGy-Eq per 30 days. For comparison, the average radiation dose from a chest X-ray is < 0.25 mGy. Analyses showed that galactic cosmic rays (GCR) is the major source, responsible for 80% or more, of radiation organ dose absorbed on the ISS. Comparisons of models to clinical data showed that space radiation effective doses can now be predicted to within about a +15% accuracy (George et al., 2011, Cucinotta et al., 2008).

Early chromosome studies strongly indicated that the radiation dose absorbed during a long-duration flight can cause quantifiable increases in chromosome damage, whereas shorter missions of a few weeks or less did not show measurable effects. These previous studies focused on the detection of dicentric chromosomes (2 partial chromosomes joined at broken ends resulting in a chromosomal structure having 2 distinct pinched areas called centromeres) which are known to decay over time with an average half-life of about 3 years, but more recent studies indicate that this rate of decay could vary greatly between individuals (Durante, 2005). In addition, follow-up measurements of chromosome damage in the blood lymphocytes by FISH from 5 months to more than 5 years after space flight revealed a time-dependent loss of "stable’" aberrations as well in blood lymphocytes, with half-lives ranging from 10 to 58 months. Current available data show that biodosimetry analyses on samples collected within a week or two of return from space provides a reliable estimate of equivalent radiation dose and risk after exposure to space radiation of a few months or more. However, retrospective doses may be more difficult to estimate because of the fairly rapid time-dependent loss of "stable" chromosomal aberrations in blood lymphocytes. Also, biodosimetry estimates from individuals who participate in repeated missions, or very long (interplanetary) missions, may be complicated by an adaptive response to space radiation and/or changes in lymphocyte survival and repopulation (George et al., 2005, 2007).

Radiation exposure for missions beyond low earth orbit will be much greater because of the absence of the magnetic protection provided by the Earth. Understanding the biological effects of such exposures and developing effective countermeasures is a major endeavor and is the focus of current international research efforts (Cucinotta, 2011).

^ back to top

Results Publications

^ back to top

Ground Based Results Publications

^ back to top

ISS Patents

^ back to top

Related Publications

^ back to top

Related Websites
ESA Erasmus Experiment Archive.
Columbus Mission - European Experiment Programme
University of Duisburg Essen

^ back to top


image Researchers use mFISH to study human chromosomal pairs. This photo shows that there has been a reciprocal exchange (translocation between chromosomes 11 and 12 and between 13 and 22) in blood lymphocytes of a crew member after space flight.
+ View Larger Image

image Classical Giemsa staining makes it possible to detect major structural changes. (a) shows normal undamaged chromosomes, (b) shows a dicentric chromosome and an associated acentric fragment indicated by arrows.
+ View Larger Image

image The mBAND method is used to detect aberrations within chromosomes as shown in the photo. An interstitial piece is lost from one of the two chromosomes 5. Image courtesy of University of Duisburg - Essen.
+ View Larger Image