Re: What roles do spindle fibers play in mitosis?

The spindle fibers are protein fillaments or protein ropes that make up an
elaborate structure called the spindle aparatus. The spindle aparatus is
critical for the separation of duplicated copies of chromosomes (very long
strands of DNA) during Mitosis.  Mitosis is the process of dividing an
already duplicated set of chromosomes into two daughter cells.  Humans, for
example, have 23 chromosomes from the mother's side and 23 chromosomes for
the father's side. Before mitosis all of these chromosomes are duplicated
during a process called DNA replication to give 92 chromosomes. The 2
duplicated identical chromosomes are called sister chromatids and are stuck
together as 46 pairs at the start of mitosis. During Metaphase of mitosis,
all of the stuck together pairs of sister chromatids are attached to
spindle fibers on either side of the pair. The spindle fibers come from
opposite ends of the cell, called the poles. When the spindle fibers attach
to the pairs from opposite ends- they push and pull the sister chromatid
pair like tug-of-war and the pair ends up exactly in the middle of the cell
in between the two poles. During Anaphase, the spindle fibers get shorter
but still are attached to the sister chromatids. When the fibers from
opposite poles shorten, the pull apart the two identical copies and each
copy moves with the fiber as it moves towards the pole.  This happens for
all the sister chromatid pairs so that 46 sigle copies of chromosomes (23
mothers/23 dads) are at each pole and there is a complete set of
chromosomes for each of the two new cells that are formed at the end of
mitosis. The spindle aparatus is an amazing structure to see in real cells.
You should look online at pictures or in a biology book. I hope this
answers your question.
Elena Rodriguez