PART A: Stages of Mitosis in my own words. 1. Interphase: DNA has formed already, but it remains in the simple form of chromatin. Chromatins are structures that are loosely coiled in the cell. 3 I also observed during my lab that this was the only stage where I could still see a nucleus and nucleolus intact within the cell; this is because it’s the only stage where the nuclear membrane has not broken apart yet to begin forming a new cell.
Prophase: In this stage the chromatin converges to create rod shaped chromosomes. The nucleus and nucleolus cannot be seen anymore. 3 3. Metaphase: Here the most noticeable change is that the chromosomes converge into the middle of the cell, forming the spindle apparatus. 3 The spindle fibers connect and attach at the very middle part of the chromosomes where they connect to each other; this spot is called the centromere. 3 4. Anaphase: In this stage the chromosomes start to separate. They separate from the centromere, and they begin to move away from one another. Now there are two separate sets of chromatin.
3 5. Telophase: Here two separate clusters of chromatin form on either opposite poles of the cell. Also here is where we can see the beginning of two separate nuclei form. Here it is apparent by my observations that this will be the last stage before the cells split, because the chromatins are completely separated now on opposite ends of the cell. 6. Daughter Cells: Now we can see that there are two completely separated cells. They have their own independent set of organelles from the original “parent” cell they came from. The cells are smaller than the original cell, about half the size of it. PART B: Differences between Plant and Animal cells. The difference between plant and animal cells during mitosis is actually not that extensive, there are only a couple areas where the process differs. First and foremost in animal cells nuclear division happens everywhere, all the time. In plants it happens only in special designated areas called meristems. Animal cells contain centrioles, which plant cells do not. The main difference observed between the two comes in the telophase stage before the cells split. Here, in animal cells a cleavage furrow forms where the cell splits, whereas with plants through the process of cytokinesis (which is the name for the actual splitting of cells in mitosis) the cell wall of the parent cell is extended to both new daughter cells. 5 This process has to be different because animal cells do not have a cell wall, but plant cells do. 5 PART C: List the Functions of Mitosis and Meiosis.
Functions of Mitosis
- Tissue Growth
- Asexual Reproduction
Functions of Meiosis
- Increases genetic variability
Questions from the Lab Manual
Is there a correlation between the number of chromosomes and the size of the organism?
No, while the amount of chromosomes can differ from organism to organism, there is no direct correlation between the organism’s size and the amount of chromosomes they contain.
Are all chromosomes the same size?
No, certain chromosomes are but not all chromosomes are the same size.
What can you infer as to the amount of genetic material per chromosome in the organisms listed in Chart 1 at the end of this exercise?
To put it simply, there is really no correlation between amount of chromosomes and size or complexity of the organism. Humans have fewer chromosomes than a spider, even though we are more complex. Another example is that a Locust has more chromosomes than a bullfrog which is much larger. 6 So there is no correlation present in the data displayed. “ANSWER THE FOLLOWING” SECTION 1.
When a primary oocyte is observed, is it a haploid or diploid? Why?
The primary oocyte would be a diploid in this case, this is because it a cell that consists and possesses two separate sets of chromosomes.
At which stage does crossing over occur?
” It happens during meiosis while in the Prophase stage.
What is the evolutionary significance of this?
This is crucial because it helps create more “genetic variability”, meaning that the organism won’t be exactly the same as the parent organism because their genetic identity changed during the crossing over process. 4 There are many reasons this is important, but the main reason is because over time it gives organism more variety, and with that a better chance to change and adapt to the ever changing scenarios and environments it interacts with around it. Without crossing over, there would be extremely limited amounts of evolution, and in turn species would not be able to have survived and adapted so well over history.
What happens to the polar bodies?
During oogenesis, the polar bodies are essentially formed as a result of the split of the original egg cell. 6 After they are created, basically as a byproduct of oogenesis, they are discarded by the egg.
What function do the polar bodies have?
The polar bodies do not really ever become a functioning part of the new cell, but they serve the purpose of extracting and discarding the extra chromosomes that the oocyte possesses, without using up an excessive amount of resources.
How many ova are produced by the meiotic division of a primary oocyte?
Just on egg, and three polar bodies that are discarded.
How many sperm are produced by the meiotic division of a primary spermatocyte?
Four sperm cells are produced from a singular meiotic division of a primary spermatocyte.
- Crossing over – Definition from Biology-Online. org. ” Life Science Reference – Biology Online. Web. 29 Sept. 2011. <http://www. biology-online. org/dictionary/Crossing_over>
- “Diploid – Definition from Biology-Online. org. ” Life Science Reference – Biology Online. Web. 29 Sept. 2011. <http://www. biology-online. org/dictionary/Diploid>
- “Function and stages of mitosis. ” Virtual Classroom Biologie. Web. 29 Sept. 2011. <http://www. vcbio. science. ru. nl/en/virtuallessons/mitostage/>
- “Meiosis. ” Suny. edu. Suny College. Web. 28 Sept. 2011. <http://faculty. lintoncc. suny. edu/faculty/michael. gregory/files/bio%20101/bio%20101%20lectures/meiosis/meiosis. htm>
- “Re: How Do Plant and Animal Mitosis Differ? ” MadSciNet: The 24-hour Exploding Laboratory. Web. 29 Sept. 2011. <http://www. madsci. org/posts/archives/2002-01/1012526835. Cb. r. html>
- Skinner-Brassard, Gail L. Life Science 1 Laboratory Student Report and Study Guide. Dubuque, IA: Kendall Hunt, 2011. Print.
- “Stages of Mitosis. ” Thinkquest. org. Web. 28 Sept. 2011. <http://library. thinkquest. org/C0118084/Gene/Chromosomal_Inheritance/StagesMitosis. htm>.