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- 1. Cell Cycle, Mitosis and Meiosis Presented By :- Vishaldeep Umare CHO,MPSPCC,M.A,B.A,Bsc(N).
- 3. The cell cycle is an ordered sequence of events that extends from the time a cell is first formed from a dividing parent cell until its own division. The cell cycle multiplies cells © 2012 Pearson Education, Inc.
- 4. During cytokinesis, the cytoplasm is divided into separate cells. The process of cytokinesis differs in animal and plant cells. Cell division is a continuum of dynamic changes
- 5. Cytokinesis Cleavage furrow Contracting ring of microfilaments Daughter cells Cleavage furrow
- 6. The cells within an organism’s body divide and develop at different rates. Cell division is influenced externally by the presence of essential nutrients, growth factors, proteins that stimulate division, there are over 50 different growth factors which work for one or more cell type density-dependent inhibition, in which crowded cells stop dividing, anchorage dependence, the need for cells to be in contact with a solid surface to divide. Anchorage, cell density, and chemical growth factors affect cell division
- 7. The cell cycle control system is a cycling set of molecules in the cell that triggers and coordinates key events in the cell cycle. Checkpoints in the cell cycle can stop an event or signal an event to proceed. Growth factors signal the cell cycle control system
- 8. There are three major checkpoints in the cell cycle. Growth factors signal the cell cycle control system G1- commitment to divide, growth factors present?, Size of cell ok?, G2- check for proper DNA replication M- all chromosomes attached to spindle fibers
- 9. Cell Cycle progresses by action of Cdks Cyclins proteins produced by the cell during cell division Cyclin-dependent kinases (Cdk) cyclin is required to activate these enzymes activates cell proteins by phosphorylating them (proteins needed for S phase) needed to go through G1 checkpoint MPF Maturation-promoting factor (mitosis promoting factor) aka Mitosis- promoting factor is a cyclin-Cdk complex phosphorylates proteins needed for mitosis needed to go through G2 checkpoint
- 10. Rate of Cell Division Differs from one cell type to the next Examples: red bone marrow cells divide every 12 hours to replace RBCs that wear out Cells at tip of root divide about every 19 hours. Neurons (nerve cells) normally never divide again once brain is fully formed in utero Control of Division, lost = CANCER Cancer is different depending on the tissue affected Common theme is lack of control over cell division Abnormal, uncontrolled cell division Mutation in genes (including p53) that target and control abnormal cells. Abnormal cells impede functioning of normal cells
- 11. p53 gene ( tumor suppressor gene) Key role in G1 checkpoint P53 protein monitors DNA Found absent or damaged in most cancer cells
- 12. Cancer is failure of cell cycle control Tumor suppressor genes- prevents the development of mutated cells, prevents cancer/tumors Oncogenes- cancer causing genes Proto-oncogenes- normal genes that become mutated
- 13. Meiosis Production/formation of __________ Basis of sexual reproduction Only germ cells undergo meiosis
- 14. Haploid gametes (n 23) Egg cell Sperm cell Fertilization n n Meiosis Ovary Testis Diploid zygote (2n 46) 2n Mitosis Key Haploid stage (n) Diploid stage (2n) Multicellular diploid adults (2n 46)
- 15. A pair of homologous chromosomes in a diploid parent cell A pair of duplicated homologous chromosomes Sister chromatids 1 2 3 INTERPHASE MEIOSIS I MEIOSIS II How meiosis halves chromosome number…
- 16. Centrosomes (with centriole pairs) Centrioles Sites of crossing over Spindle Tetrad Nuclear envelope Chromatin Sister chromatids Fragments of the nuclear envelope Centromere (with a kinetochore) Spindle microtubules attached to a kinetochore Metaphase plate Homologous chromosomes separate Sister chromatids remain attached Chromosomes duplicate Prophase I Metaphase I Anaphase I INTERPHASE: MEIOSIS I: Homologous chromosomes separate
- 17. Prophase II Metaphase II Anaphase II MEIOSIS II: Sister chromatids separate Sister chromatids separate Haploid daughter cells forming Telophase II and Cytokinesis
- 18. Meiosis Leads to Genetic Diversity Three ways genetic diversity is increased by meiosis: 1. 2 parents contribute ½ of the genetic material to offspring 2. Crossing-over in Prophase I 3. Chromosome Alignment in Metaphase I Meiosis produces cells that are NOT identical, unique gametes
- 19. Tetrad (pair of homologous chromosomes in synapsis) Breakage of homologous chromatids Joining of homologous chromatids Chiasma Separation of homologous chromosomes at anaphase I Separation of chromatids at anaphase II and completion of meiosis Parental type of chromosome Recombinant chromosome Recombinant chromosome Parental type of chromosome Gametes of four genetic types 1 2 3 4 C c e E C c e E c e C E C e e C E c c E C E C e c E e c Crossing Over increases genetic diversity by producing “new” chromosomes.
- 20. Independent orientation at metaphase I Independent orientation of chromosomes in meiosis and random fertilization lead to varied offspring
Editor's Notes
- #3: Teaching Tips 1. The authors note in Module 8.4 that each of your students consists of about 10 trillion cells. It is likely that this number is beyond comprehension for most of your students. Consider sharing several simple examples of the enormity of that number to try to make it more meaningful. For example, the U.S. population in 2011 is about 312 million people. To give every one of those people about $32,000, we will need a total of 10 trillion dollars. Here is another example. If we gave you $32,000 every second, it would take 10 years to give you 10 trillion dollars. The US Debt Clock helps relate these large numbers to the US national debt at www.usdebtclock.org. 2. In G1, the chromosomes have not duplicated. But by G2, chromosomes consist of sister chromatids. If you have created a demonstration of sister chromatids, relate DNA replication and sister chromatids to the cell cycle.
- #4: Teaching Tips Students might keep better track of the sequence of events in a cell cycle by simply memorizing the letters IPPMAT: the first letters of interphase, prophase, prometaphase, metaphase, anaphase, and telophase are represented in this acronym.
- #5: Figure 8.6A Cleavage of an animal cell
- #6: Teaching Tips Students who closely examine a small abrasion on their skin might notice that the wound tends to heal from the outer edges inward. This space-filling mechanism is a natural example of density-dependent inhibition, which is also seen when cells in a cell culture dish stop dividing when they have formed a complete layer.
- #7: Teaching Tips The cell cycle control system depicted in Figure 8.8A is like the control device of an automatic washing machine. Each has a control system that triggers and coordinates key events in the cycle. However, unlike a washing machine, the components of the control system of a cell cycle are not all located in one place.
- #8: G1 checkpoint allows entry into the S phase or causes the cell to leave the cycle, entering a nondividing G0 phase. G2 checkpoint, and M checkpoint. Teaching Tips The cell cycle control system depicted in Figure 8.8A is like the control device of an automatic washing machine. Each has a control system that triggers and coordinates key events in the cycle. However, unlike a washing machine, the components of the control system of a cell cycle are not all located in one place.
- #9: G1 checkpoint allows entry into the S phase or causes the cell to leave the cycle, entering a nondividing G0 phase. G2 checkpoint, and M checkpoint. Teaching Tips The cell cycle control system depicted in Figure 8.8A is like the control device of an automatic washing machine. Each has a control system that triggers and coordinates key events in the cycle. However, unlike a washing machine, the components of the control system of a cell cycle are not all located in one place.
- #14: Figure 8.12A The human life cycle
- #15: Figure 8.12B How meiosis halves chromosome number
- #16: Figure 8.13_left The stages of meiosis: Interphase and Meiosis I
- #17: Figure 8.13_4 The stages of meiosis: Meiosis II
- #19: Figure 8.17B How crossing over leads to genetic recombination
- #20: Teaching Tips 1. The possible number of combinations produced by independent orientation of human chromosomes at meiosis metaphase I is 223 or 8,388,608. This number squared is more than 70 trillion. The authors rounded down to 8 million for 223 and squared this, to estimate 64 trillion possible combinations. But more precisely, the number of possible zygotes produced by a single pair of reproducing humans, based solely on independent assortment and random fertilization, is over 70 trillion! 2. Another way to represent the various combinations produced by independent orientation of chromosomes at meiosis metaphase I continues the shoe analogy. Imagine that you have two pairs of shoes. One pair is black, the other is white. You want to make a new pair drawing one shoe from each original pair. Four possible pairs can be made. You can have (1) the left black and left white, (2) the right black and right white, (3) the left black and right white, or (4) the right black and left white. Actually using two pairs of shoes from your students can inject humor and create a concrete example that reduces confusion. For an additional bit of humor, ask the class if 46 students want to contribute their shoes as you try to demonstrate all 8,388,608 combinations!