Mitosis

A Day in the Life of a Cell.....

View thismedia type="custom" key="4377927" on mitosis. Of course, if you want to actually HEAR the video, YOU MUST HAVE EARPHONES. Otherwise, turn off your audio. Today begins our study of cell division. We will first look at mitosis, which is [|asexual reproduction].
 * Activity One **

1. stony corals 2. sponges 3. flatworms 4. starfish
 * Describe the process by which each of the following organisms reproduces:
 * Explain **how** each of the above processes is asexual reproduction.

Activity Two While human beings do not reproduce by mitosis, the growth and repair of cells in humans is accomplished by mitosis. Mitosis is the dividing phase of the [|cell cycle]. 1. What are the three stages of the cell cycle? 2. Interphase is divided into four sub-phases: What happens during each of these sub-phases? 3. What is the M-phase? 4. What kind of cell activity signals the cell to begin dividing? 5. Cell signaling instructs the cell to stop dividing. What is this? How does it work? 6. Gene P53 is responsible for turning off mitosis. How is this accomplished? 7. What happens if P53 fails to work properly? 8. Certain cells, such as neurons, spend their lives in G-0. What does this mean? 9. Most cells spend their non-dividing lives in G-1. What does this mean?
 * G-0
 * G-1
 * S
 * G-2

Activity Three

The dividing phase of the cell cycle is called [|mitosis]. 1. What are the phases of mitosis? **(Note: prometaphase is not a phase that you may have studied previously. This is an in-between stage that occurs between prophase and metaphase and completes the part of the process begun in prophase. Some geneticists do not break prophase down into two parts. Instead, they consider prophase an exceptionally long phase that ends with the beginning of metaphase. I think it is important that we include prometaphase as a separate entity simply because prophase encompasses so many parts of the process and takes such a long time to be accomplished.)** 2. According to the author of the above website, when does prophase end and prometaphase begin? 3. The spindle fibers consist of kinetechore and nonkinetechore fibers. What is the difference between the two? 4. The kinetechore spindle fibers permit the chromatids to do what in metaphase? 5. We have used the words chromosome and chromatid interchangeably so far. What do you think is the difference between the two terms? 6. What is the significant event of metaphase? 7. What signals the beginning of anaphase? 8. By the time telophase has ended, cytokinesis is also complete. Describe the events of both these phases.

Activity Four **Your teacher will distribute a worksheet for the next activity.** The following four websites are to use in conjunction with your worksheet:
 * The [|Cells Alive!] site
 * The [|San Diego State University] site
 * The [|John Kyrk] site
 * The [|University of Arizona] site

**Now that you have the individual phases of mitosis and the cell cycle down pat, let's take a deeper look:**
 * Remember that the process of mitosis is not a series of stopping and starting. Once mitosis has begun, each phase is part of a [|continuous stream of movement]. In other words, metaphase does not stop when the chromatids are aligned at the metaphase plate; as soon as the chromatids are aligned, they begin movement toward the opposite poles (anaphase). It is at this point that we stop using the term chromatids and start using the term chromosomes. Mitosis is complete only at the end of [|cytokinesis], unless the two daughter cells are going to divide again. If they are going to divide again, the cell will enter G-1 stage of interphase. If the daughter cells are not programmed to divide again, they will enter a period of dormancy called G-0.

**
 * **In what phase is the cell shown above left? This is one of the [|checkpoints of the cell cycle].**
 * **Why is this considered a checkpoint?**
 * **What are the other checkpoints?**
 * **What proteins control the activities of the cell cycle?**

Activity Five
 * And finally .......Work through this [|tutorial] of mitosis and the cell cycle. Don't forget to [|test yourself] when you have finished the tutorial.

Play [|mitosis battleship].

Activity Six Test Friday, October 23.

[|This review] includes pictures of the individual stages of both plant and animal cells.

Work through this [|picture tutorial] and identify each stage of the process.

How does cell surface area relate to its volume? How does this affect cell division? Check out [|this website] that graphically explains the relationship between surface area and volume. Remember that during G-1 phase of interphase, the cell volume increases as more organelles, more membrane, and more proteins are produced in preparation for cell division. How could the change in ratio affect the cell's ability to conduct business across the cell membrane

Activity Seven - Project Watch this [|video] before reading your project information.

Project Outline** 1. Imagine that you are on the board of directors for a new biotechnology firm working in the field of tissue engineering. As a board member, you must write a letter to the head of the company explaining your position about this research. In developing your position, you must consider the following issues:


 * The practicality of this research
 * The long-term benefits of this research
 * The long-term risks of this research
 * An assessment of the long-term prospects for this research

The following websites should provide information on tissue engineering:
 * http://en.wikipedia.org/wiki/Tissue_engineering
 * [|tissue engineering]
 * [|wise geek]
 * [|termis site]
 * http://tissue.medicalengineer.co.uk/Advantages+and+Disadvantages+of+Tissue+Engineering.php

This is by no means an exhaustive list of websites; Google "tissue engineering" and read journal articles, newspaper articles and any other media where this type of information would be chronicled or archived.

2. Before you write your letter, you must have formed an opinion about your topic. Be sure you have considered the following questions:
 * Why might tissue regeneration be an improved method for healing injuries?
 * What are some methods of creating living tissue?
 * What is meant by the term "tissue engineering?"
 * Who will benefit from this research?
 * Which body tissues have already been engineered and used as replacement tissue?
 * What implications does this research have for the future?
 * Should government fund this research? Why or why not? (this doesn't have to be part of your letter but it is a question you should consider)

3. When you have written your letter, exchange letters with your partner. You should critique each other's papers not so much for grammar or spelling but as to the clarity of your letter and whether or not you have demonstrated understanding of the topic. Within the body of the paper, you should have clearly explained the long-term risks and benefits of this research and developed a well researched letter that is supported by substantial evidence. This means that you must quote or reference reputable sources.

4. When your partner has finished critiquing your letter, revise it, polish it, and be sure to spell and grammar check your document. Your finished document should also include a bibliography of at least three separate, reliable sources. Remember that Google.com is a search engine and Wikipedia.com is an online encyclopedia; you may NOT cite them as sources.

The purpose of this project is to introduce you to a fast-growing biotechnological field that is surrounded, as is so often the case, by controversy and debate.

View the [|rubric] for this letter.


 * Scheduled completion date: October 29, 2009.**