Mitosis. Fluorescence micrograph of chromosomes (blue) during prometaphase of mitosis (nuclear division). During mitosis two daughter nuclei are formed from one parent nucleus. Before prometaphase, chromosomes condense into defined units, allowing organised and equal segregation into daughter cells. Chromosomes are made up of two identical chromatids, joined at a centromere (red). The bright green areas are green fluorescent protein (GFP), which is derived from jellyfish. GFP has been attached to aurora b protein kinase, a protein that is thought to be vital for the proper condensation of chromosomes.