Chapter 11

Summary		Questions		Media Resources
11.1 Bacteria divide far more simply than do eukaryotes.
• Bacterial cells divide by simple binary fission. • The two replicated circular DNA molecules attach to the plasma membrane at different points, and fission is initiated between those points.		1. How is the genome replicated prior to binary fission in a bacterial cell?		•Prokaryotes
11.2 Chromosomes are highly ordered structures.
· All eukaryotic cells contain chromosomes but they vary in the number of chromosomes. · Eukaryotic DNA forms a complex with histones and other proteins and is packaged into chromosomes.		2. What are nucleosomes composed of, and how do they participate in the coiling of DNA? 3. What is a karyotype? How are chromosomes distinguished from one another in a karyotype?		•DNA Packaging •Cell Division Introduction •Chromosomes
11.3 Mitosis is a key phase of the cell cycle.
• In eukaryotic cells, DNA replication is completed during the S phase of the cell cycle, and during the G2 phase the cell makes its final preparation for mitosis. Along with G1, these two phases constitute the portion of the cell cycle called interphase. • The first stage of mitosis is prophase, during which the mitotic spindle apparatus forms. • In the second stage of mitosis, metaphase, the chromosomes are arranged in a circle around the periphery of the cell. • At the beginning of the third stage of mitosis, anaphase, the centromeres joining each pair of sister chromatids separate, freeing the sister chromatids from each other. • After the chromatids physically separate, they are pulled to opposite poles of the cell by the microtubules attached to their centromeres. • In the fourth and final stage of mitosis, telophase, the mitotic apparatus is disassembled, the nuclear envelope re-forms, and the chromosomes uncoil. • When mitosis is complete, the cell divides in two, so that the two sets of chromosomes separated by mitosis end up in different daughter cells.		4. Which phases of the cell cycle is generally the longest in the cells of a mature eukaryote? 5. What happens to the chromosomes during S phase? 6. What changes with respect to ribosomal RNA occur during prophase? 7. What event signals the initiation of metaphase? 8. What molecular mechanism seems to be responsible for the movement of the poles during anaphase? 9. Describe three events that occur during telophase. 10. How is cytokinesis in animal cells different from that in plant cells?		•Mitosis Overview •Plant Cell Mitosis •Mitosis •Mitosis •Activity: Mitosis • Nuclear Division in Drosophila • Cell Cycle
11.4 The cell cycle is carefully controlled.
• The cell cycle is regulated by two types of proteins, cyclins and cyclin-dependent protein kinases, which permit progress past key "checkpoints" in the cell cycle only if the cell is ready to proceed further. • Failures of cell cycle regulation can lead to uncontrolled cell growth and lie at the root of cancer.		11.  What aspects of the cell cycle are controlled by the G1, G2, and M checkpoints? How are cyclins and cyclin-dependent protein kinases involved in cell cycle regulation at checkpoints?		•Exploration: Regulating the Cell Cycle • Cell Cycle Control

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