Chapter 9 Cell Cycle and Cellular Reproduction AP

Chapter 9: Cell Cycle and Cellular Reproduction AP Biology Mr. Freidhoff

9. 1 Chromosomes • Chromosome: Tightly packed DNA and protein structure. • Histone: Protein molecule that DNA wraps itself around. • Chromatin: Thin thread of DNA. Condenses before mitosis. Consists of DNA and packaging proteins.

9. 1 Chromosomes • Chromatid: Arm of Chromosome, made of DNA double helix. • After replication, chromosome doubles the amount of DNA. • Sister Chromatids: Identical DNA strands that remain attached until mitosis.

9. 1 Chromosomes • Centromere: Sister chromatids are attached at region with many DNA repeats. • Kinetochores: Regions on the centromere where spindle fibers will attach.

9. 1 Chromosomes • Diploid (2 n): Number of average chromosomes in a somatic cell. Includes two chromosomes of each kind. • Haploid (n): Cells that contain only one of each chromosomes. • Sperm and Egg. • Homologous Chromosome: Pair of chromosomes with the identical genes in the same order.

9. 2 The Cell Cycle • Cell Cycle: Set of stages that take place when a cell divides.

9. 2 The Cell Cycle • Interphase • Most of the cell cycle is spent in interphase. • Cell performs normal functions. • Three parts of Interphase: G 1, S, G 2

9. 2 The Cell Cycle • G 1 (Growth or Gap phase) • Recovers from previous division. • Grows in size. • Increase the number of organelles. • Accumulates materials for DNA synthesis. • Chromosome is NOT condensed.

9. 2 The Cell Cycle • S Phase • Synthesis or Replication Phase • Before S phase, DNA chromosomes are composed of one double helix. • After S phase, the DNA is composed of strands of identical DNA. • Chromosome is NOT condensed.

9. 2 The Cell Cycle • G 2 Phase: • Cell synthesizes proteins that assist in cell division. • Ex: Microtubules • Centriole replication complete. • Chromosome is NOT condensed.

9. 2 The Cell Cycle • Go Phase: “Lazy Phase” • Cell continues normal functions, doesn’t divide. • Nerve cells, muscle cells, etc. • Control of cell division.

9. 2 The Cell Cycle • M phase • Mitosis: Nuclear Division • Cytokinesis: Division of Cytoplasm • Chromosome is condensed.

9. 3 Mitosis • Centrosome: Main microtubuleorganizing center of the cell. • Only have one centrosome until S phase. • Centrioles: Barrel shaped organelles found in pairs at right angles. • Located next to Nucleus. • Organizes mitotic spindle which are fibers of microtubules. • Anchor cytoskeleton into membrane.

9. 3 Mitosis • Prophase: • Chromatin have condensed. • Chromosomes composed of duplicated chromatid. No orientation. • Nuclear membrane starts to break down. • Aster: Microtubules that come out of centrioles. Make star like pattern.

9. 3 Mitosis • Prometaphase: • Kinetochores on each side of centromere appear. • Spindle fibers attach to kinetochores. • Chromosomes still aren’t oriented.

9. 3 Mitosis • Metaphase: • Centromeres of Chromosomes are aligned along middle of the cell called the metaphase plate. • M-Phase Checkpoint • Cell checks to make sure spindle fibers is attached to each kinetochore.

9. 3 Mitosis • Anaphase: • Sister chromatids separate. • Spindle fibers shorten pulling chromatids to poles of the cell. • Shortest phase.

9. 3 Mitosis and Cytokinesis • Telophase: • Spindle fibers dissemble. • Nuclear envelope starts to form around chromosomes. • Chromosomes start to unwind.

9. 3 Mitosis • Cytokinesis: • Division of cytoplasm. • When Cytokinesis doesn’t occur, results in multinucleated cell.

9. 3 Mitosis • Animal: Cleavage furrow forms from microfilament ring constricting. • Plant: Vesicles that contain cell wall components help form cell plate which creates new membrane.

9. 4 Cell Cycle Regulation • Growth Factors: Signals received by proteins in the plasma membrane to divide.

9. 4 Cell Cycle Regulation • Cyclins: Internal signaling proteins that increase or decrease the amount of cellular division that occurs. • Cdk, Cyclin Dependent Kinases: Enzymes, always present, need activated by cyclin proteins.

9. 4 Cell Cycle Regulation • G 1 Checkpoint • Checks to make sure the cell has enough room and organelles to replicate.

9. 4 Cell Cycle Regulation • Apoptosis: Programmed cell death. • Caspases are enzymes, usually inhibited, that break down internal and external structures. • Cell loses contact with neighboring cells, nucleus fragments, membrane develops blisters and get broken down.

9. 4 Cell Cycle Regulation • G 2 Checkpoint • Checks if DNA replication has finished. • Also checks DNA for Damage.

9. 4 Cell Cycle Regulation • Mitotic Phase Checkpoint • Cell checks if chromosomes have attached correctly to mitotic spindle.

9. 4 Cell Cycle Regulation • p 53: Stops cell division if DNA is damaged. • p 53 tries to initiate DNA repair at first. Can also stop cell cycle, called cell growth arrest. • If large amounts of mutations occur, p 53 will initiate apoptosis.

9. 5 Cancer • Cancer: Uncontrolled cell growth. • Caused by mutations on genes that control cell division. • Great variation within types of cancer. • Benign Growth: Tumor that lacks ability to migrate. • Malignant Growth: Cancerous cells spreading.

9. 5 Cancer • Cancer cells lack differentiation. • Don’t contribute to the overall function of tissue. • Cancer cells have abnormal number of nuclei. • Abnormal amount of chromosomes.

9. 5 Cancer • Cancer cells do not undergo apoptosis. • Controlled cell death doesn’t occur. • Cancer cells form tumors. • Cancer cells pile on top of each other.

9. 5 Cancer • Cancer cells undergo metastasis and angiogenesis. • Metastasis: Cancer cells move around the body causing the cancer to spread. • Angiogenesis: formation of blood vessels into tumor. Allows cancer to spread.

9. 5 Cancer • Mutations on genes that signal cell division cause problems. • Proto-oncogenes: Genes that codes for proteins that promote the cell cycle and prevent apoptosis. Become oncogenes. • Analogy: Gas pedal of a car. • Tumor Suppressor Genes: genes that code for proteins that inhibit the cell cycle and promote apoptosis. • Analogy: Brakes of a car.

9. 5 Cancer • Telomeres: Ends of chromosomes that protect the inner most part of a chromosome. • Repeated DNA that does not code for any genes. • As a cell divides, ends of the telomere get cut off. • If a telomere gets cut down to nothing, it stops dividing. • Mutations in genes that code for enzymes that elongate telomeres might cause cancer.