Cell Repair and Growth (Adib Azad)

Title: Cell Repair and Growth with an Onion

Principle(s) Investigated: Cell Structure and Function

Standards: MS-LS1-2: Develop and use a model to describe the function of a cell as a whole and ways parts of cells contribute to the function.

Materials: Onions; Microscopes; Microscope Slides, Mitosis Video

Procedure: Students will observe and interpret the tip of an onion root.

1. Watch the video.
2. Students will first get a prepared mount of an onion root tip.
3. They will then observe different stages of cell development (mitosis phases).
4. Students then will interpret them in the context of cellular growth and repair.
5. Students will then build a model of cell growth and its applications to the body.

Student prior knowledge: What prior concepts do students need to understand this activity?

• Students should be aware that cell repair in the body is fueled by the food the body eats through the work of both the digestive and circulatory systems. Students should also understand the difference between observation and inference. Students should know that genetic information is stored in the nucleus of cells.

Explanation:

The aim of the lesson is to establish that the process of mitosis is necessary for cells and our bodies to grow and repair themselves. Through the use of an onion root tip students can visualize and observe stages of mitosis. Students can then interpret their observations to determine that mitosis is the driving force of cellular growth. The lesson can be applied to a discussion of the skeletal system through the phenomena of a broken bone repairing itself. Before doing this lesson students need to have an understanding of the role of food in the body and the functions of the digestive and circulatory systems. Using the knowledge from this lesson and previous ones students can develop a model that answers the question "How do our bodies heal?"

Questions & Answers:

1. Name an application of mitosis in our bodies.
2. When our bodies are tired, mitosis starts to rebuild our muscles stronger than before because our original cells have been damaged and need repair.
3. What makes onion root tip an ideal place to look for mitosis? Where else would be a good place to look?
4. Onion root tip, and most plant root tips, are always growing and so will always have cells in various stages of mitosis. Bone marrow and stomach lining would be a good place to look for cells undergoing mitosis because that would be where cell division occurs frequently.
5. Why might muscles and bones grow stronger with exercise or breaking?
6. As the body grows and repairs and itself more cells are than there previously were making the entire areaof tissues stronger than it previously was.

Applications to Everyday Life: Knowing how cells grow and reproduce is applicable to a variety of phenomena. It explains how our bodies can heal after taking damage. Knowing the specific mechanisms behind mitosis and cell repair is useful to scientists who wish to develop better treatment procedures. Understanding that mitosis is a driver for cell and body growth can also be useful to scientists who wish to develop products that encourage growth. Knowing the stages of mitosis can help explain meiosis which in turn can be of great use in the development of fertility treatments.

Photographs: Phases of Mitosis: