Chromatids (2n = 8), stained purpleNucleiContractile ringMitochondria, shared outA 14 µm rounded animal cell (ruler: 1 tick = 1 µm) with 2n = 8 chromosomes, as in the fruit fly. Mitosis takes about an hour (shown about 250× faster): the chromosomes condense in prophase, the envelope breaks and the spindle captures every kinetochore, all eight line up on the metaphase plate, then the sisters are pulled apart in about five minutes and an actomyosin ring pinches the cell in two, each daughter half the volume (0.79× the radius) and roughly half the mitochondria.
~60 min哺乳动物细胞 M 期M phase in a mammalian cell~5 min后期姐妹染色单体分离anaphase: sister chromatids separate~1 µm/min染色体被拉向两极的速度speed chromosomes are pulled poleward2^(−1/3)子细胞半径比 = 0.79daughter radius ratio = 0.79~37 trillion人体约有的细胞数（~37 万亿）cells in a human body