Lab 8, Mitosis and Meiosis

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Julie Lake
November 8, 2012
BIO 111, C11- Online
Villalpando, Shawn
Lab 8
Title: Mitosis and Meiosis
Exercise 1: Mitosis in Animal and Plant Cells
Questions:
A.) What is the purpose of mitosis?
The purpose of mitosis is to create or produce more cells for a living organism. Mitosis occurs when genetic substance in the nucleus divides or separates in order to create more cells. Cytokinesis normally occurs next and the single cell develops into two separate cells. This same process continues to occur over and over creating more cells for an organism replacing old or dead cells. B.) What other term is commonly used in place of “mitosis”? Another commonly used term for “mitosis” is “cell division”, because the division of cells is what occurs during the process of mitosis. C.) What is blastula?

Blastula is the end of the cleavage furrow stage in the cell division process when there is a collection or ball of cells. D.) What are the differences in the mitotic processes between animal and plant cells? The difference between the mitotic processes of animal and plant cells are that animal cells have a cleavage furrow at the end of the telophase and cytokinesis phases and plant cells have a cell plate. E.) Why might there be more mitotic division in an onion root tip than in other areas of the plant? There is usually more mitotic division in an onion root tip than in other areas of the plant because the tip of the plant is where the new growth is occurring and cells are dividing and creating more cells. F.) A summary of mitosis – fill in the correct answer. The nucleus in the undivided cell has the diploid (2n) number of chromosomes, and the nuclei in the two split cells also have __the same___ number of chromosomes. In mitosis, the chromosome number (check the correct choice) __X___ stays the same or _____ halves. Results:

For both the whitefish and the onion, what is the 2n number of chromosomes that were observed? HINT: separate chromosomes are easiest to view and count during Prometaphase. The number of chromosomes observed in the whitefish and the onion were 23 or 46.

Observations:
Whitefish Blastula cells:

Onion Root Tip cells:

Exercise 2: Meiosis in Animals
Questions:
A. Which organ, the ovary or the testes, contained the greater number of gametes? The organ that contained the greater number of gamets is the testes. B. What may be a reason for this?
The eggs in the ovary are much larger than the sperm in the testes and it takes numerous sperm trying to get to the egg before one actually does fertilize the egg and most of the sperm die trying. Observations:

Ovary:

Testis:

Exercise 3: Simulating Meiosis
Questions:
A. What does mitosis accomplish?
The process of mitosis accomplishes replacing old or dying cells in an organism by replicating the DNA and cell division. B. When and where does mitosis occur?
Mitosis occurs in eukaryotic cells during the interphase of cell division. C. What does meiosis accomplish?
Meiosis has two consecutive cell divisions that produce a total of four genetically different daughter cells. D. When and where does meiosis occur?
Meiosis occurs in the ovaries and testes or reproduction organs during interphase. E. How do these two processes differ?
Mitosis creates identical cells to replace old or dying cell tissue while Meiosis occurs in the sexual reproduction organs and creates genetically different cells. F. How do Prophase in Mitosis and Prophase I in Meiosis differ? In mitosis chromosomes create two sister chromosomes during the prophase and in meiosis the homologous chromosome pair is held together by chiasm and cohesion during prophase I. G. Does Meiosis occur anywhere else in the body besides within the gonads? Meiosis occurs in the reproduction organs, therefore it only in the gonads (ovaries and testes). H. How does meiosis confer advantages to an organism when compared to asexual reproduction such as budding? Meiosis...
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