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1. What do you think of when you hear the phrase "cell cycle"?

2. What do you know about the cell cycle?

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The process by which cells divide and make new cells.

There are several phases the cell undergoes during the cell cycle:

Interphase

Mitosis

Cytokinesis

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The first phase of the cell cycle.

Consists of three phases:

Gap 1 (G1)

Normal cell conditions.

Synthesis (S)

DNA replication occurs

Gap 2 (G2)

The cell grows and prepares for division.

Ensures both daughter cells can survive after division

Organelle and protein production.

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The phase of the cell cycle that involves the division of the nucleus.

This process consists of four different stages:

Prophase

Metaphase

Anaphase

Telophase

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The first stage of mitosis.

The nuclear membrane dissolves.

It will come back later!

The chromatin condenses into chromatids.

Spindle fibers are formed.

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The second phase of mitosis.

The chromosomes line up at the metaphase plate.

The spindle fibers attach to the centromeres of the chromosomes.

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The third phase of mitosis.

The spindle fibers separate the sister chromatids to opposite sides of the cell.

The cell begins to stretch.

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The fourth phase of mitosis.

Nuclear membrane reforms.

The chromatids decondense into chromatin.

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The final stage of cell division.

The division of the cytoplasm.

Cleavage furrow occurs.

The parent cell splits into two identical daughter cells.

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The Biology Project > > Activity Cell Biology > Intro to Onion Root Tips Activity

Online Onion Root Tips

Determining time spent in different phases of the cell cycle

Growth in an organism is carefully controlled by regulating the cell cycle. In plants, the roots continue to grow as they search for water and nutrients. These regions of growth are good for studying the cell cycle because at any given time, you can find cells that are undergoing mitosis.

In order to examine cells in the tip of an onion root, a thin slice of the root is placed onto a microscope slide and stained so the chromosomes will be visible. The cells you'll be looking at in this activity were photographed with a light microsope and then digitized so you can see them on the computer.

Although slicing the onion root captures many cells in different phases of the cell cycle, keep in mind that the cell cycle is a continuous process. Scientists have divided the process into 5 phases, each characterized by important events, but these divisions are still arbitrary.

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Vocabulary
The Biology Project > > Activity Cell Biology > Intro to Onion Root Tips Activity

CREDITS

The Biology Project
The University of Arizona
Revised: April 2004
Revised: August 2004
Contact the Development Team

http://www.biology.arizona.edu
All contents copyright © 1997-2004. All rights reserved.

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The Biology Project > > Activity Cell Biology > Intro to Onion Root Tips Activity Growth in an organism is carefully controlled by regulating the cell cycle. In plants, the roots continue to grow as they search for water and nutrients.

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1. What are the stages of mitosis?

2. What stage of mitosis involves the spindle fibers attaching to the centromeres?

3. What is the first stage of the cell cycle?

4. In what phase does DNA replication occur? Be specific.

5. Illustrate the process of mitosis.

6. Compare and contrast mitosis with interphase.

7. Compare and contrast the the genetic material of each stage of mitosis.