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5.1: Cell Division and the Cell Cycle

Difficulty Level: At Grade Created by: CK-12
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Key Concept

Cell division is part of the life cycle of cells. The cell cycle also includes phases of growth and DNA synthesis. Regulatory proteins normally control the cell cycle at key checkpoints. Cancer is a disease that occurs when the cell cycle is no longer regulated.


  • CA.9–12.IE.1.d; CA.9–12.LS.1.c
  • NSES.9–12.A.1.1, 4, 6; NSES.9–12.C.1.4, 6
  • AAAS.9–12.5.C.4, 5

Lesson Objectives

  • Contrast cell division in prokaryotes and eukaryotes.
  • Identify the phases of the eukaryotic cell cycle.
  • Explain how the cell cycle is controlled.
  • Define cancer, and relate it to the cell cycle.

Lesson Vocabulary

  • binary fission: type of cell division that occurs in prokaryotic cells in which a parent cell divides into two identical daughter cells
  • cancer: disease that occurs when the cell cycle is no longer regulated and cells divide out of control
  • cell cycle: repeating series of events that a cell goes through during its life, including growth, DNA, synthesis, and cell division
  • cell division: process in which a parent cell divides to form two daughter cells
  • cytokinesis: splitting of the cytoplasm to form daughter cells when a cell divides
  • DNA replication: process of copying of DNA prior to cell division
  • interphase: stage of the eukaryotic cell cycle when the cell grows, synthesizes DNA, and prepares to divide
  • mitosis: process in which the nucleus of a eukaryotic cell divides
  • tumor: abnormal mass of cells that may be cancerous

Teaching Strategies

Introducing the Lesson

Tell students that each of them started out as a single cell smaller than the period at the end of a sentence. Now, each of them consists of trillions of cells. Ask them to explain how they developed from one cell to trillions of cells. (Sample answer: The single cell divided, then those two cells divided, and so on.) Tell the class they will learn how cells divide in this chapter.


Demonstrate cell division by binary fission. At the URL below, students can watch a video of a paramecium dividing, “rock-and-roll” style. After the video, call on students to describe what they observed and relate it to the steps of binary fission described in the lesson.

Differentiated Instruction

Encourage students to make their own cycle diagram of the eukaryotic cell cycle, using Eukaryotic Cell Cycle from the FlexBook® textbook as a basis. Tell students to add sketches, key words, or examples to their diagram to help them understand and remember the phases of the cycle. ELL, LPR, SN


Chemistry students might be interested in knowing more about regulatory proteins and how they control the cell cycle. Direct them to the URLs below. After they develop more in-depth knowledge, ask them to teach the topic to the rest of the class.

Science Inquiry

Have students do the online onion root tip activities at the URL below. Onion root tip cells are a model system for viewing the phases of the cell cycle. Students will observe prepared slides of root tip cells and tally the number and percent of cells in each phase of the cycle. Then they will use the data to determine the length of each phase.

Health Connection

Expand on the connection between regulation of cell division and cancer that is introduced in the lesson. Explain how mutations in proto-oncogenes and tumor-suppressor genes lead to unregulated cell growth and cancer. The diagram and first two URLs below provide background information on the topic. The third URL provides student animations and activities relating to cancer and the cell cycle. It provides a teacher’s guide as well.

  1. http://biology.kenyon.edu/courses/biol114/Chap07/Chapter_07.html
  2. http://science.education.nih.gov/supplements/nih1/cancer/guide/understanding1.htm
  3. http://science.education.nih.gov/supplements/nih1/cancer/default.htm

Reinforce and Review

Lesson Worksheets

Copy and distribute the lesson worksheets in the CK-12 Biology Workbook. Ask students to complete the worksheets alone or in pairs as a review of lesson content.

Review Questions

Have students answer the Review Questions listed at the end of the lesson in the FlexBook®.

Points to Consider

When a eukaryotic cell divides, the nucleus divides first in the process of mitosis.

  • What do you think happens during mitosis? Can you predict what molecules and cell structures are involved in this process?
  • How do you think mitosis might differ from binary fission? What steps might be involved in mitosis?

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