Reading: The Complete Cycle

This video reviews all the steps of mitosis; seeing it all together is a great review at this stage.

Practice

This diagram shows the five phases of mitosis and cytokinesis. During prophase, the chromosomes condense and become visible, spindle fibers emerge from the centrosomes, the nuclear envelope breaks down, and the nucleolus disappears. During prometaphase, the chromosomes continue to condense and kinetochores appear at the centromeres. Mitotic spindle microtubules attach to the kinetochores, and centrosomes move toward opposite poles. During metaphase, the mitotic spindle is fully developed, and centrosomes are at opposite poles of the cell. Chromosomes line up at the metaphase plate and each sister chromatid is attached to a spindle fiber originating from the opposite pole. During anaphase, the cohesin proteins that were binding the sister chromatids together break down. The sister chromatids, which are now called chromosomes, move toward opposite poles of the cell. Non-kinetochore spindle fibers lengthen, elongating the cell. During telophase, chromosomes arrive at the opposite poles and begin to decondense. The nuclear envelope reforms. During cytokinesis in animals, a cleavage furrow separates the two daughter cells. In plants, a cell plate separates the two cells.

Figure 2. Karyokinesis (or mitosis) is divided into five stages—prophase, prometaphase, metaphase, anaphase, and telophase. The pictures at the bottom were taken by fluorescence microscopy (hence, the black background) of cells artificially stained by fluorescent dyes: blue fluorescence indicates DNA (chromosomes) and green fluorescence indicates microtubules (spindle apparatus). (credit “mitosis drawings”: modification of work by Mariana Ruiz Villareal; credit “micrographs”: modification of work by Roy van Heesbeen; credit “cytokinesis micrograph”: Wadsworth Center/New York State Department of Health; scale-bar data from Matt Russell)

 

Which of the following is the correct order of events in mitosis?

  1. Sister chromatids line up at the metaphase plate. The kinetochore becomes attached to the mitotic spindle. The nucleus reforms and the cell divides. Cohesin proteins break down and the sister chromatids separate.
  2. The kinetochore becomes attached to the mitotic spindle. Cohesin proteins break down and the sister chromatids separate. Sister chromatids line up at the metaphase plate. The nucleus reforms and the cell divides.
  3. The kinetochore becomes attached to the cohesin proteins. Sister chromatids line up at the metaphase plate. The kinetochore breaks down and the sister chromatids separate. The nucleus reforms and the cell divides.
  4. The kinetochore becomes attached to the mitotic spindle. Sister chromatids line up at the metaphase plate. Cohesin proteins break down and the sister chromatids separate. The nucleus reforms and the cell divides.

Check Your Understanding

Answer the question(s) below to see how well you understand the topics covered in the previous section. This short quiz does not count toward your grade in the class, and you can retake it an unlimited number of times.

Use this quiz to check your understanding and decide whether to (1) study the previous section further or (2) move on to the next section.