The Steps Of Mitosis | Biology For Non-Majors I - Lumen Learning

Mitosis is an incredible process with precise steps and regulation. Without mitosis, life would be impossible. However, the process can seem a bit complex.

To begin, let’s explore the different stages of mitosis.

Prophase is the first stage of mitosis. In prophase,

• chromosomes condense and become visible
• spindle fibers emerge from the centrosomes
• nuclear envelope breaks down
• nucleolus disappears

Prometaphase is the second stage of mitosis. In prometaphase,

• chromosomes continue to condense
• kinetochores appear at the centromeres
• mitotic spindle microtubules attach to kinetochores
• centrosomes move toward opposite poles

Metaphase is the third step in mitosis. In mitosis,

• mitotic spindle is fully developed, centrosomes are at opposite poles of the cell
• chromosomes are lined up at the metaphase plate
• each sister chromatid is attached to a spindle fiber originating from opposite poles

Anaphase is the fourth step in mitosis. In anaphase,

• cohesin proteins binding the sister chromatids together break down
• sister chromatids (now called chromosomes) are pulled toward opposite poles
• non-kinetochore spindle fibers lengthen, elongating the cell

Telophase is the fifth step in mitosis. In telophase,

• chromosomes arrive at opposite poles and begin to decondenese
• nuclear envelope material surrounds each set of chromosomes
• the mitotic spindle breaks down

Cytokinesis is the sixth and final step of mitosis. In cytokinesis,

• Animal cells: a cleavage furrow separates the daughter cells
• Plant cells: a cell plate separates the daughter cells

Mitosis

Now that we’ve reviewed each of the steps, let’s look at the cycle as a whole:

Mitosis: In Summary

In prophase, the nucleolus disappears and chromosomes condense and become visible. In prometaphase, kinetochores appear at the centromeres and mitotic spindle microtubules attach to kinetochores. In metaphase, chromosomes are lined up and each sister chromatid is attached to a spindle fiber. In anaphase, sister chromatids (now called chromosomes) are pulled toward opposite poles. In telophase, chromosomes arrive at opposite poles, and nuclear envelope material surrounds each set of chromosomes. Finally, in cytokenesis, the two daughter cells are separated.

Let’s take a quick quiz to review what we’ve just learned!

Practice Quiz

Which of the following options shows the correct order of the steps of mitosis?

1. prophase, prometaphase, metaphase, anaphase, telophase, and cytokinesis.
2. metaphase, prometaphase, prophase, anaphase, telophase, and cytokinesis.
3. prophase, prometaphase, metaphase, telophase, anaphase, and cytokinesis.

Show Answer

Answer a is correct. If you answered b, you might be having some trouble keeping the beginning steps in order. If you answered c, you might be having some trouble keeping the steps in the second half of mitosis in order.

What step of mitosis is shown here?

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The cell shown above is in prophase. In prophase, the first step in mitosis, the nuclear envelope breaks down and chromosomes condense and become visible.

What step of mitosis is shown here?

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The cell shown above is in metaphase. In metaphase, the mitotic spindle is fully developed, centrosomes are at opposite poles of the cell, and chromosomes are lined up at the metaphase plate.

Which step does the following passage describe?

The kinetochores appear at the centromeres, the mitotic spindle microtubules attach to kinetochores, and the centrosomes move toward opposite poles.

Show Answer

This passage describes prometaphase, the second step in mitosis

What occurs during anaphase?

1. Each sister chromatid (or chromosome) is attached to a spindle fiber originating from opposite poles
2. Sister chromatids (or chromosomes) are pulled toward opposite poles
3. Sister chromatids (or chromosomes) arrive at opposite poles and begin to decondense

Show Answer

Answer b is correct. This is one of the events that occur during anaphase. During anaphase, the cohesin proteins binding the sister chromatids together also break down, and the non-kinetochore spindle fibers lengthen, elongating the cell.

Answer a occurs during metaphase, which happens before anaphase. Answer c occurs during telophase, which happens after anaphase.

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.

Show Answer

Answer d is correct.