Chapter 9: The Cell Cycle
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(2) What is the Cell Cycle? • Ordered sequence of events in the life of a eukaryotic cell..
(3) Cell Growth and Reproduction • Cells make up multicellular organisms that come in a variety of sizes and shapes – Elephant vs. Mouse (both multicellular). • Out of what we have discussed, give me something that may limit the size of a cell?.
(4) Cell Growth and Reproduction • Diffusion limits cell size – Diffusion is fast and efficient over short distances – Over larger distances, diffusion is inefficient. • What does this mean?? – SURFACE TO VOLUME RATIO! • If Mitochondrion is in center of a really large cell, it will take a LONG time for molecules to reach it! If cell is small, it doesn’t take long—DIFFUSION LIMITS CELL SIZE!.
(5) Cell Growth and Reproduction. Vs.. This also explains why organisms can’t be just one giant-sized cell!.
(6) Cell Growth and Reproduction • DNA limits cell size – Nucleus contains blueprints for cell proteins – There is a limit of how quickly proteins can be copied and made in nucleus.
(7) Cell Growth and Reproduction • If this giant amoeba has up to 1000 nuclei, how does this benefit the organism?.
(8) Cell Growth and Reproduction • Large amounts of DNA in many nuclei ensures that cell activities are carried out quickly and efficiently.
(9) Cell Growth and Reproduction • Cell Cycle: Sequence of growth and division of the cell. • Majority of cell’s life is spent during INTERPHASE or the cell’s growth period. Interphase.
(10) Why do cells divide? 1. Replace dead or damaged cells 2. Cell getting too large: division will increase the diffusion rate (increases the surface area to volume ratio).
(11) G 1: Cycle Begins. Gap 1 Phase:. First growth stage. G0: Non-dividing cells.
(12) G1: First Growth • Cells are growing and synthesizing: – Proteins – RNA – Macromolecules. • G0 Cells—still growing, but NOT able to complete the cell cycle..
(13) G 1:. G0: Non-dividing cells. Cycle Begins. Gap 1 Phase:. First growth stage. Restriction Point.
(14) Reaching the Restriction Point the point of no return…. • Cell receives signal to undergo division (Cell is getting too large, neighboring cells have died, etc.) • G1 Checkpoint—the cell is large enough & conditions are appropriate. • Once the cell passes the restriction point, it must complete the cell cycle before returning to G1 or G0..
(15) G 1:. G0: Non-dividing cells. Cycle Begins. Gap 1 Phase:. Restriction Point. First growth stage DNA Synthesis: DNA is replicated S:.
(16) Reviewing the Structure….
(17) What Does DNA Look Like in the Nucleus? • Specific packaging and organization of DNA in the nucleus. • Chromosome = highest level of organization. • DNA double helix = smallest level • Double helix is wrapped around small proteins called histones. Help to organize and make DNA very compact!.
(18) DNA Replication: Notes (back of Cell Cycle sheet) Where does DNA Replication take place? – Nucleus of cell!. Three Basic Steps to the Process: 1. Unwind the double-helix 2. Bind enzymes to pre-existing DNA. 3. Synthesize new matching strand with old strand..
(19) G 1:. G0: Non-dividing cells. Cycle Begins. Gap 1 Phase:. Restriction Point. First growth stage DNA Synthesis: DNA is replicated S:. Gap Phase 2: Second Growth Stage G 2:.
(20) G2: Second Growth Stage • Cell continues to grow • Must pass the G2 checkpoint to continue – Did the DNA duplicate? – Is cell large enough? – Is the environment suitable?.
(21) G 1:. G0: Non-dividing cells. Cycle Begins. Gap 1 Phase:. Restriction Point. First growth stage M: Nuclear Division. DNA Synthesis: DNA is replicated S:. Gap Phase 2: Second Growth Stage G 2:.
(22) How do the daughter cells at the end of mitosis and cytokinesis compare with their parent cell when it was in of the cell cycle? A. The daughter cells have half the amount of cytoplasm and half the amount of DNA. B. The daughter cells have half the number of chromosomes and half the amount of DNA. C. The daughter cells have the same number of chromosomes and half the amount of DNA. D. The daughter cells have the same number of chromosomes and the same amount of DNA..
(23) Mitosis: Period of Cell Division • Forms two daughter cells (identical) with complete set of chromosomes – FOUR PHASES: • Prophase • Metaphase • Anaphase • Telophase.
(24) Why do chromosomes coil during mitosis? A. to increase their potential energy B. to allow the chromosomes to move without becoming entangled and breaking C. to allow the chromosomes to fit within the nuclear envelope D. to allow the sister chromatids to remain attached.
(25) Cell Growth and Reproduction • 1st Phase of Mitosis: PROPHASE – Long stringy chromatin coils up into visible chromosomes. Spindle fibers Disappearing nuclear envelope Doubled chromosome.
(26) Cell Growth and Reproduction • 1st Phase of Mitosis: PROPHASE – Each duplicated chromosome is made of two halves called SISTER CHROMATIDS. Sister chromatids.
(27) Cell Growth and Reproduction • 1st Phase of Mitosis: PROPHASE – Sister chromatids held together by CENTROMERE • Plays role in chromatid separation. Centromere.
(28) Cell Growth and Reproduction • 1st Phase of Mitosis: PROPHASE *****Nucleus begins to disappear as nuclear envelope and nucleolus disintegrate ****Centrioles begin to migrate to opposite ends of cells.
(29) End of Part 1.
(30) The centromere is a region in which A. chromatids remain attached to one another until anaphase. B. metaphase chromosomes become aligned at the metaphase plate. C. chromosomes are grouped during telophase. D. the nucleus is located prior to mitosis..
(31) If there are 20 chromatids in a cell, how many centromeres are there? A. B. C. D.. 10 20 30 40.
(32) Cell Growth and Reproduction • 2nd Phase of Mitosis: METAPHASE – Doubled chromosomes attach to spindle fibers by centromeres – Chromosomes pulled up by spindle fibers and begin to line up on equator of spindles.
(33) Cell Growth and Reproduction • 2nd Phase of Mitosis: METAPHASE – What is the importance? ******This arrangement of the chromatids ensures that each new cell receives identical and complete set of chromosomes (DNA).
(34) The region labeled A in Figure 9-1 is called the A. B. C. D.. centromere centriole. sister chromatid. spindle.
(35) The structures labeled B in Figure 9-1 are called A. B. C. D.. Centrosomes Centrioles Sister chromatids Spindles.
(36) During which phase(s) of mitosis are structures like the one shown in Figure 9-1 visible? A. B. C. D.. anaphase and prophase prophase and metaphase metaphase only anaphase and interphase.
(37) Cell Growth and Reproduction • 3rd Phase of Mitosis: ANAPHASE – Beginning of sister chromatid separation ***Centromeres split ***Chromosomes separate from each other ***Shortening of spindle fibers pull apart chromatids to opposite poles.
(38) Which term describes centromeres uncoupling, sister chromatids separating, and the two new chromosomes moving to opposite poles of the cell?. A. B. C. D.. telophase anaphase prometaphase metaphase.
(39) Cell Growth and Reproduction • 4th Phase of Mitosis: TELOPHASE ***Begins once chromatids reach opposite poles ***Chromosomes begin to to unwind ***Spindle breaks down.
(40) Cell Growth and Reproduction • 4th Phase of Mitosis: TELOPHASE – Nucleolus and nuclear envelope reappears around new set of chromosomes – Double membrane forms between two new nuclei – Two daughter cells formed.
(41) Which of the following is a correct statement about the events of the cell cycle? A. Little happens during the G1 and G2 phases. B. DNA replicates during cytokinesis. C. The M phase is usually the longest phase. D. Interphase consists of the G1, S, and, G2 phases..
(42) Regarding mitosis and cytokinesis, one difference between higher plants and animals is that in plants A. the spindles contain microfibrils in addition to microtubules, whereas animal spindles do not contain microfibrils. B. sister chromatids are identical, but they differ from one another in animals. C. a cell plate begins to form at telophase, whereas in animals a cleavage furrow is initiated at that stage. D. chromosomes become attached to the spindle at prophase, whereas in animals chromosomes do not become attached until anaphase..
(43) Cell Growth and Reproduction • Cytokinesis: – After Telophase, cell’s cytoplasm divides – Animal Cells: • plasma membrane pinches off forming two separate cells.. – Plant Cells: • Cell plate laid across cell’s equator—there is no pinching off. • Cell membrane forms around each cell and new cell walls form on each side of cell plate.
(44) Cytokinesis: The Conclusion of Mitosis • Cell plate forms in plant cell, separating the two daughter cells. – Vesicles deliver the materials. • Daughter cells from animal cell division pinch apart..
(45) G 1:. G0: Non-dividing cells. Cycle Begins. Gap 1 Phase:. Restriction Point. First growth stage M: Nuclear Division. DNA Synthesis: DNA is replicated S:. Cycle Begins Over!!! Gap Phase 2: Second Growth Stage G 2:.
(46) Which event occurs during interphase? A. The cell carries out metabolic processes, such as growth. B. Centrioles, made from amino acids begin to appear. C. Spindle fibers begin to form from proteins. D. Centromeres, that are attached to the chromosomes divide..
(47) Cytokinesis usually, but not always, follows mitosis. If a cell completed mitosis but not cytokinesis, the result would be a cell with. A. a single large nucleus. B. high concentrations of actin and myosin. C. two abnormally small nuclei. D. two nuclei. E. two nuclei but with half the amount of DNA..
(48) Which term describes centrioles beginning to move apart in animal cells? A. B. C. D.. telophase anaphase prophase metaphase.
(49) If cells in the process of dividing are subjected to colchicine, a drug that interferes with the functioning of the spindle fibers, at which stage will mitosis be arrested?. A. B. C. D.. interphase telophase anaphase metaphase.
(50) One difference between cancer cells and normal cells is that cancer cells. A. are unable to synthesize DNA. B. are arrested at the S phase of the cell cycle. C. continue to divide even when they are tightly packed together. D. cannot function properly because they are affected by density-dependent inhibition. E. are always in the M phase of the cell cycle..
(51) Cancer is a disease in which some cells lose the ability to control their A. B. C. D.. Size Spindle fibers Rate of division Surface area.
(52) DNA Mutations • A mutation occurs whenever a change in the genetic sequence occurs (recall activity). – Not always harmful – However, they play a large role in disease and the development of cancer. • Other errors by environmental factors – chemicals or radiation (includes Ultraviolet radiation!).
(53) DNA Repairs • Proof-reading process—to detect & correct errors – DNA polymerase checks & corrects. • Excision Repairs– When single nucleotide bases are mismatched, found and replaced with the correct base (all done with enzymes). What changes might a mutation have on an organism? – Taking a look at Sickle Cell Anemia & Tay-sachs disease.
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