Courtesy: National Human Genome Research Institute
Polar fibers are microtubules that play a very important role in the cell division processes of both mitosis and meiosis. Shaped like hollow rods, polar fibers are spindle fibers that extend from the two poles of a dividing cell and help to manipulate and separate chromosomes.
For example, during metaphase of mitosis, polar fibers extend from the cell poles to align chromosomes at the metaphase plate. In anaphase, polar fibers connected to chromosomes shorten thereby separating sister chromatids and pulling them toward the spindle poles. Polar fibers not connected to chromosomes lengthen and elongate the cell.