Twenty-three pairs of chromosomes locked within our cells hold the key to the development of the human body. Today, on World Down Syndrome Day, it’s pair number 21 that draws our attention. A developmental defect called trisomy 21 means each human cell ends up with not two, but three, copies of chromosome 21. This results in Down syndrome; a condition characterised by a delay in mental development, short stature and a distinct set of facial characteristics. Heart and immune system defects are also often found and may be explained by differences at the level of cells – specifically, endothelial progenitor cells (EPCs) that circulate in the blood. Scientists found fewer EPCs in individuals with Down Syndrome, and those present were more sensitive to stress and infection. Electron microscopy shows abnormalities in their appearance too – the EPCs (pictured) are larger and have more vacuoles (white spaces) than normal cells.
Written by Lux Fatimathas
BPoD stands for Biomedical Picture of the Day. Managed by the MRC London Institute of Medical Sciences the website aims to engage everyone, young and old, in the wonders of biomedicine. Images are kindly provided for inclusion on this website through the generosity of scientists across the globe.