In prophase, chromosomes become visible as distinctive structures. In metaphase of mitosis, the chromosomes line up single file along the equator of the cell. This aligning of chromosomes at the equator is believed to result from the action of spindle fibers, which are attached to a protein structure called the kineto-chore at the centromere of each chromosome (fig. 3.29).
Anaphase begins when the centromeres split apart and the spindle fibers shorten, pulling the two chromatids in each chromosome to opposite poles. Each pole therefore gets one copy of each of the forty-six chromosomes. During early telophase, division of the cytoplasm (cytokinesis) results in the production of two daughter cells that are genetically identical to each other and to the original parent cell.
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This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.