As they move, they pull the one copy of each chromosome with them to opposite poles of the cell. The spindle tubules then shorten and move toward the poles of the cell.
As mitosis progresses, the microtubules attach to the chromosomes, which have already duplicated their DNA and aligned across the center of the cell. These tubules, collectively known as the spindle, extend from structures called centrosomes - with one centrosome located at each of the opposite ends, or poles, of a cell. Early microscopists were the first to observe these structures, and they also noted the appearance of a specialized network of microtubules during mitosis. The word 'mitosis' means 'threads,' and it refers to the threadlike appearance of chromosomes as the cell prepares to divide. Mitosis is the process in which a eukaryotic cell nucleus splits in two, followed by division of the parent cell into two daughter cells.
