Abstract
Experimental study was made by keeping human peripheral blood lymphocytes under simulated microgravity in a Rotary Cell Culture System bioreactor to investigate the changes that occur in the number of chromosomes, the expression rate of chromosome fragile site, and the expressions of DNA replication- and repair-related genes. Experimental results indicate simulated microgravity has no effect on the numerical chromosome instability of human peripheral blood lymphocytes, but it enhances the structural chromosome instability of human peripheral blood lymphocytes through the inhibition of DNA replication and the reduction of DNA repair. So, the mechanism of chromosome fragile site induced by simulated microgravity can be explained using the changes that occur in the chromosome structure of human peripheral blood lymphocytes, the DNA replication and repair under the effect of simulated microgravity.