Q: What are the five stages that mitosis is conventionally broken down into?
A: Prophase, Prometaphase, metaphase, anaphase, and telophase.
Q: What is G1 phase?
A: This part of cell cycle is where the cell spends most of its functional life. This is the time when the cells are performing their assigned tasks, metablizing, synthesizing etc. At some point in the cycle something triggers the cell to being a cell division event.
Q: How are cancer cells different from normal cells?
A: If and when normal cells stop dividing, cancer cells do so at random points in the cycle, rather than at the normal checkpoints. Moreover, cancer cells can go on dividing indefinitely in culture if they are given a continual of nutrients; in essence, they are "immortal."
1. Cell division results in genetically identical daughter cells.
2. The mitotic phase alternates with interphase in the cell cycle.
3. The eukaryotic cell cycle is regulated by a molecular control system.
4. In each generation of humans, meiosis reduces the chromosome number from 46 to 23. Fertilization fuses two gametes together and returns the chromosome number to 46, and mitosis conserves that number in every somatic cell nucleus of the new individual.
5. It is hypothesized that mitosis had its origins in simpler prokaryotic mechanisms of cell reproduction.
Figure 12.5 The Cell Cycle
In a dividing cell, the mitotic (M) phase alternates with interphase, a growth period. The first part of interphase (G1) is followed by the S phase, when the chromosomes replicate; G2 is the last part of interphase. In the M phase, mitosis divides the nucleus and distributes its chromosomes to the daughter nuclei, and cytokinesis divides the cytoplasm, producing two daughter cells. The relative durations of G1, S, and G2 may vary.
The eukaryotic cell cycle is divided into four phases: M(mitosis), G1(the period between mitosis and the initiation of nuclear DNA replication), S(the period of nuclear DNA replication), G2(the period between the completion of nuclear DNA replication andmitosis).
Chromosome: a cellular structure carrying genetic material, found in the nucleus of eukaryotic cells. Each chromosome consists of one very long DNA molecule and associated proteins. (A bacterial chromosome usually consists of a single circular DNA molecule and associated proteins. It is found in the nucleoid region, which is not membrane bounded.)
Somatic Cells:
Gamete: a haploid reproductive cell, such as an egg or sperm. Gametes unite during sexual reproduction to reproduce a diploid zygote.
Chromatin: the complex of DNA and proteins that makes up a eukaryotic chromosome. When the cell is not dividing chromatin exists in its dispersed form, as a mass of very long, thin fibers that are not visible with a light microscope.
Cytokinesis: the division of the cytoplasm to form two separate daughter cells immediately after mitosis, meiosis I, or meiosis II.
Cleavage: the process of cytokinesis in animal cells, characterized by pinching of the plasma membrane.
Binary fission: a method of asexual reproduction by "division in half." In prokaryotes, binary fission does not involve mitosis; but in single-celled eukaryotes that undergo binary fission, mitosis is part of the process.
Mitotic spindle: an assemblage of microtubles and associated proteins that is involved in the movements of chromosomes during mitosis.
Checkpoint: a control point in the cell where stop and go-ahead signals can regulate the cycle.
Kinetochore: a structure of proteins attached to the centromere that links each sister chromatid to the mitotic spindle.
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