Stages of Mitosis

INTERPHASE: During late interphase, the nucleus is well defined and surrounded by the nuclear envelope. It contains one or more nucleoli. Just outside the nucleus are two centrosomes, formed duirng early interphase by replication of a single centrosome.Microtubules extend from the centrosomes in a radial array called asters.The chrosomsomes have already duplicated but are still in the form of loosely packed chromatin fibers.

PROPHASE: During the prophase the nucleoli in the nucleus disappear. The chromatin fibers become tightly ccoiled and condense into chromosomes. Chromosomes line up in pairs and are joined at the centromere. In the cytoplasm, the spindle fibers begin to form and are made of microtubules. The centrosomes move away from each other, propelled by the lengthening microtubules, or spindle fibers, between them.
METAPHASE: The centromes are at opposite ends of the cell poles. The chromosom es are lined up at the 'metaphase plate', an imaginary line equidistant between the two poles. The centromeres of the chromosomes are all aligned with one another. The chromatids are of each chromosomes are attached to a microtubule which form the spindle.
ANAPHASE: The paired chromosomes separate. They move along the microtubules toward opposite poles of the cell. The poles move farther apart. By the end of anaphase, the two poles of the cell each have a complete set of chromosomes.
TELOPHASE: The microtubules become even longer, and daughter nuclei begin to form at the two poles of the cell. Nuclear envelopes are formed, the nucleoli reappear, the chromatin of the chromosomes uncoils. Mitosis is now complete: one nucleus has divided into two genetically identical nuclei. Cytokinesis follows and involves the formation of a cleavage furrow, which pinches the cells in two



These pages authored and maintained by Marcella Dawson. Revised 3/2002 . Copyright 1995 CRPC GirlTECH. All rights reserved. . Email your comments. These pages were developed through GirlTECH '96, a teacher training and student technology council program sponsored by the Center for Research on Parallel Computation (CRPC), a National Science Foundation Science and Technology Center.