Chapter 12 – The Cell Cycle – Pages 215-229
The Key Roles of Cell Division
1. Explain how cell division functions in reproduction, growth, and repair.
2. Describe the structural organization of the genome.
3. Describe the major events of cell division that enable the genome of one cell to be passed on to the daughter cells.
4. Describe how the chromosome number changes throughout the human life cycle.
the Mitotic Cell Cycle
5. List the phases of the cell cycle and describe the sequence of events that occurs during each phase.
6. List the phases of mitosis and describe the events characteristic of each phase.
7. Recognize the phases of mitosis from diagrams and micrographs.
(there will be diagrams on this test)
8. Draw or describe the spindle apparatus, including centrosomes, kinetochores microtubules, nonkinetochore microtubules, asters, and centrioles (in animal cells)
9. Describe what characteristic changes occur in the spindle apparatus during each phase of mitosis.
Starts in Prophase- The formation starts with the centrosome which is associated with the centrioles in animal cells but not plant cells. This area is the organization area, called the "microtubule-organizing center" Centrosomes(during interphase) replicate and when they move to opposite poles of the cell as they start at the nucleus, the spindle fibers grow from the centrosomes. The name of centrosomes changes here to spindle poles.(end of prometaphase) Attached to the center of the sister chromatids are centromeres which also has a kinetochore also made of proteins and some choromsomal DNA that seem to regulate the pulling of chromosomes. There are kinetochores that aren't associated with the centromeres and they are called nonkinetochores. First the kineochores play a "tug of war" until they reach the center. The nonkinetochores are also attached to microtubules but these tend to overlap at the midpoint which is called the metaphase plate.(now we are metaphase) As soon as anaphase begins the proteins which were holding the sister chromatids together are now inactive.
10. Explain the current models for poleward chromosomal movement and elongation of the cell's polar axis.
Kinetochores have motor proteins that "walk" a chromosome along a microtubule(like a tight rope, or when you have a rope to guide you along a path) The microtubules also shorten up depolymerizing(break down into smaller subunits.)
Nonkinetochore microtubules actually move past each other during anaphase and they lengthen by adding the protein tubulin.
11. Compare cytokinesis in animals and plants.
In animal cells a cleavage furrow forms and is a pinching in of the two prospective daughter cells. This starts near the metaphase plate and proteins actin and myosin work together as a drawstring to pull the two cells together and then separating into two new cells. In plant cells a cell plate forms and this is derived from the Golgi Apparatus. The Golgi produce vesicles which move to towards the center along microtubules and this is the beginning of the formation of a cell plate. This plate grows and then fuses with the cell membrane and then two daughter cells are formed.
12. Describe the process of binary fission in bacteria and how this process may have evolved in eukaryotic mitosis. Regulation of the Cell Cycle.
Originally in the 1960's it was thought that after the circular DNA replicated that the cell divided and this was binary fission. Now it is thought that there is an origin of replication and as soon as the DNA replicates it begins to divide and this goes on quickly. Sort of like what happens in eukaryotic cells which may show an evolutionary connection to bacteria and the evolution of eukaryotic cells. Two intermediate examples of cell division are in dinoflagellates, where the nuclear envelope remains intact and the replicated chromosomes are attached and then separate as the cell elongates before cell division. The second example is diatoms which has an intact nuclear envelope and a spindle within the nucleus separates the chromosomes.
Evolution, Unity, and Diversity
13. Describe the roles of checkpoints, cyclin, CDk, and MPF in the cell cycle control system.
CDk's are cyclin-dependent kinases
MPF Maturation-promoting factor or mitosis promoting factor
14. Describe the internal and external factors that influence the cell cycle control system.
Science as a Process
15. Explain how the abnormal cell division of cancerous cells differs from normal cell division.