Module 5 Cell Division

This module is about cycles. Our body cells all follow a cycle. No doubt somewhere in your childhood you skinned your knee or cut your finger. Once the tears were done and the bandage was applied, you were probably told it will just take some time to heal. Over time, our cells are constantly growing and dividing to replace what is old or damaged. Skin cells can replace themselves every three days. Cells of the digestive tract and respiratory tract replace themselves rapidly because of the damage they experience from every day use. Muscle cells are much slower to replace, and bones can take months to heal.

Our life is part of a cycle too. In the previous unit you studied in detail how human life begins. In this module, you will learn how other organisms may follow similar or very different patterns in reproduction. As you consider your own family, every one is at a different stage in their life cycle, and so are the cells within their bodies.

What would happen if we could step outside of one of these cycles? What would it be like to get our cell lines to stop growing older? To simply grow and reproduce at the same rate as when we’re twenty? Aside from the social implications there may be very serious biological implications to consider. Cancer cells are in essence our own body cells that no longer respect the cell cycle. They reproduce as quickly as they can and never stop. Clearly cancerous cells are not the target of the anti-aging industry! As you continue through this module think about the internal clock that governs your cell reproduction and aging. How important is it for you to try to beat aging?

As you explore healthy and unhealthy or uncontrolled cell cycles, you will focus on the big question of how cellular processes allow for growth, healing and reproduction in the support of survival of living organisms.

This module will explore the following focusing questions:

• What structures pass genetic information on to the next generation and in what ways can cells ensure they are passed on successfully?
• What are the stages and phases of the cell cycle and do they change with age?
• How do meiosis and mitosis compare in the creation of new cells?
• When is consistency desired over variation, and which processes ensure the proper outcome?
• What differences exist between fraternal and identical twins?
• How do chromosome disorders occur and why does their occurrence increase with age?
• What are the advantages or disadvantages of different reproductive strategies?

This module relies on prior knowledge of the cell and how it works. If you feel you need to review the concepts of the cell before you begin this module, read pages 546 and 547 in your textbook. If you are comfortable with your knowledge of the cell, continue on with the module.