Microscope Investigation: Mitosis of Onion Root Tip and Whitefish Blastula

While we are into microscope mode we can take the time and effort to re-examine the cell division cycle in eukaryotes – mitosis.

First take the time to view the life cycle of a cell. You do not need to memorize the last section of the animation about the control of the cell cycle BUT it is good for you to appreciate how PROTEINS are responsible for controlling the cycle. Let me repeat – PROTEINS control the cell cycle. This is an example of how DNA controls cellular actions VIA protein synthesis.

Click me.

Then lets review mitosis. You examined this in good detail back in grade 10. IPMAT-C: Interphase, prophase, metaphase, anaphase, telophase, cytokinesis.

  • Q: What is the whole point of this process and how can we state these steps have a selective advantage and were selected FOR?

Here is the video clip.

Click me.

Task 2: [#1 was the viewing of prokaryotic and eukaryotic cells and analysis of size]

There are two commonly used cell types to view mitosis.

  1. area of growth in the root tip meristem of onion.
    • The meristem is the region of high cell division/growth in plants. They are found in the root tips and shoot tips.
  2. cell division during the development of the whitefish blastula.
    • the blastula is an early stage of animal development from about the 16 to 64 cell stage. [the 4th and 5th cell division]

The duration, that is the relative length of time, for each stage of mitosis to occur can be estimated by counting the number of cells in each stage of mitosis.

Example:

if 20 cells are counted and find: 5 in interphase, 3 in prophase, 4 in metaphase, 4 in anaphase and 4 in telophase. Then 5/20 is 1/4 of the cell cycle is spent in interphase.

I challenge you, this time, to collect data to demonstrate if the duration of mitosis in the onion root tips and whitefish blastula are equal or different. Use the proper statistical analysis to substantiate your claim.

In your blog, show state a summary of mitosis, a table of original data, the analysis of the data and a simple conclusion.

Resources to help identify cell stages:

  • Has whitefish and onion root tip images of each stage: click me
  • Has whitefish images of each stage: click me
  • has animation of this lab [minus the statistics]: http://uccpbank.k12hsn.org/courses/APBioI/course%20files/multimedia/lesson17/1002ap_4.swf

IB Expectations:

2.5 Cell division (2) hours

2.5.1 Outline the stages in the cell cycle, including interphase (G1, S, G2), mitosis and cytokinesis. (2)

2.5.2 State that tumors (cancers) are the result of uncontrolled cell division and that these can occur in any organ or tissue. (1)

2.5.3 State that interphase is an active period in the life of a cell when many metabolic reactions occur, including protein synthesis, DNA replication and an increase in the number of mitochondria and/or chloroplasts. (1)

2.5.4 Describe the events that occur in the four phases of mitosis (prophase, metaphase, anaphase and telophase). (2)

Include supercoiling of chromosomes, attachment of spindle microtubules to centromeres, splitting of centromeres, movement of sister chromosomes to opposite poles, and breakage and re-formation of nuclear membranes. Textbooks vary in the use of the terms chromosome and chromatid. In this course, the two DNA molecules formed by DNA replication are considered to be sister chromatids until the splitting of the centromere at the start of anaphase; after this, they are individual chromosomes. The term kinetochore is not expected. Aim 7: Students could determine mitotic index and fraction of cells in each phase of mitosis. Individual groups could paste data into a database. Pie charts could be constructed with a graphing computer program. If a graphing computer program is used in DCP for internal assessment, it should be according to the IA and ICT clarifications.

2.5.5 Explain how mitosis produces two genetically identical nuclei. (3)

2.5.6 State that growth, embryonic development, tissue repair and asexual reproduction involve mitosis. (1)

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