Mitosis or Meiosis?
This represents a tiny embryo just beginning to form. Once an egg is fertilized, the resulting single cell must divide many, many times to develop a fetus. Both mitosis and meiosis involve cell division; is this type of cell division an example of mitosis or meiosis? The answer is mitosis. With each division you are making a genetically exact copy of the parent cell, which only happens through mitosis.
Mitosis vs. Meiosis
Mitosis, meiosis, and sexual reproduction are discussed at http://www.youtube.com/watch?v=kaSIjIzAtYA (18:23).
Both mitosis and meiosis result in eukaryotic cells dividing. So what is the difference between mitosis and meiosis? The primary difference is the differing goals of each process. The goal of mitosis is to produce two daughter cells that are genetically identical to the parent cell, meaning the new cells have exactly the same DNA as the parent cell. Mitosis happens when you want to grow, for example. You want all your new cells to have the same DNA as the previous cells. The goal of meiosis, however, is to produce sperm or eggs, also known as gametes . The resulting gametes are not genetically identical to the parent cell. Gametes are haploid cells, with only half the DNA present in the diploid parent cell. This is necessary so that when a sperm and an egg combine at fertilization , the resulting zygote has the correct amount of DNA—not twice as much as the parents. The zygote then begins to divide through mitosis.
Pictured below is a comparison between binary fission ( Figure below ), which is cell division of prokaryotic organisms, mitosis, and meiosis. Mitosis and meiosis are also compared in the table that follows ( Table below ).
A comparison between binary fission, mitosis, and meiosis.
|Purpose:||To produce new cells||To produce gametes|
|Number of cells produced:||2||4|
|Rounds of Cell Division:||1||2|
|Haploid or Diploid:||Diploid||Haploid|
|Daughter cells identical to parent cells?||Yes||No|
|Daughter cells identical to each other?||Yes||No|
- binary fission : Reproduction through growth and division of the cell, as in bacteria.
- daughter cells : Cells that result from division of the parent cell during mitosis or meiosis.
- diploid : Having two sets of chromosomes; 2n .
- fertilization : Union of a sperm and egg.
- gamete : Sex cell, such as sperm or egg.
- haploid : Having one set of chromosomes, as in sperm and egg; n .
- meiosis : Process in cell division that reduces the chromosome number in order to make gametes.
- mitosis : Process in cell division during which the nucleus divides so that a new cell is produced that is identical to the parent cell.
- zygote : Cell that forms when a sperm and egg unite; the first cell of a new organism.
- The goal of mitosis is to produce a new cell that is identical to the parent cell.
- The goal of meiosis is to produce gametes that have half the DNA of the parent cell.
Use the resources below to answer the questions that follow.
- Mitosis and Meiosis Simulation at http://www.youtube.com/watch?v=zGVBAHAsjJM (11:53)
- What are homologous chromosomes?
- How do the location of specific genes compare between homologous chromosomes?
- How does meiosis differ between females and males? Why do you think this is? Explain your reasoning as much as possible.
- How Cells Divide at http://www.pbs.org/wgbh/nova/body/how-cells-divide.html
- How many daughter cells arise from mitosis? How many daughter cells are produced in meiosis?
- How is the location of the chromosomes during prophase of mitosis different from their location during prophase I of meiosis? Why is this difference significant?
- How does the attachment of spindle fibers differ between mitosis and meiosis?
- Is anaphase I or anaphase II in meiosis more analogous to anaphase in mitosis? Explain your reasoning.
- How many steps are there in mitosis? How many steps are there in meiosis?
- How does interphase I of meiosis differ from interphase II of meiosis?
- What is the goal of mitosis? Of meiosis?
- How many cells are created during mitosis? During meiosis?