Cell division occurs through mitosis and meiosis. Mitosis produces two daughter cells that are identical to the parent cell. It occurs in somatic cells and involves the stages of interphase, prophase, metaphase, anaphase and telophase. Meiosis produces gamete cells with half the number of chromosomes and involves two cell divisions that result in four daughter cells. Gametogenesis refers to the specific meiotic processes of spermatogenesis in males and oogenesis in females that produce sperm and egg cells.

1. Cell Growth and Division

2. Cell Division is the Cell’s way of Reproducing itselfReproductionis a Life Process more of the same unit is formed not essential for survival is a need to perpetuate species

3. Chapter ObjectivesAt the end of lecture discussion, the learners are expected to:Explain Cell Reproduction at the molecular level, with emphasis of the role of DNA and Chromosomes

4. Describe the limits to cell growth.Identify the types of cells in the body of an organism.Name and describe the sequence of stages in Mitosis and Meiosis.

5. Describe the chromosamal changes in Mitosis and Meiosis. Give the significance of cell division.Trace the formation of sperm and egg cells through the process of spermatogenesis and oogenesis.

6. Cell Growth & Reproduction

7. Review of TermsDNAChromatidsHistonesHelixChromosomeChromatinNucleosomes

8. DNA ReplicationDNA possesses a remarkable ability to create copies of its own structure

9. DNA Replication cont’REPLICATIONOccurs as the double strand of DNA unzips at certain points(synthesis stage)

10. Limits of Cell GrowthCells of human adult are no larger than human babies.Cells eat and defecateCells know to adaptCells growth and division rate vary.Sometimes cell growth and division become uncontrollable (cancer cells)

11. Cells of the Human BodySomatic CellsDiploid number (2N) or complete set of (46) ChromosomesEx. Skin Cells Lung Cells etc.Reproductive CellsHaploid number (N) or half (23) number of chromosomes.Ex. Sperm Cell Egg Cell

12. Assessment BreakExplain the limits of Cell Growth.Why do cells divide?Distinguish betweenSomatic and Germ CellsHaploid and Diploid

13. MITOSISDuring Mitosis Chromosomes duplicate and daughter cells receives the same amount of chromosomal material as the parent cell.Mitosis is the first step in growth and differentiation of somatic cells.

14. MITOSIS cont’InterphaseG1 ~ Presynthetic S ~ Synthetic Phase G2 ~ Postsynthetic stage

15. Interphase( not a phase of Mitosis)Growth occurs as organelles double (G1)Chromosomes (DNA) duplicates (S)Growth occurs as cell prepares to divide (G2)

16. The Major Events of Cell DivisionKaryokinesisSplitting of the nucleusInside nuclear events of the cellCytokinesisCytoplasmic DivisionOutside nuclear events of the cell

17. Mitosis

18. Phases of MitosisMitosis begins after InterphaseStages/Phases Prophase Metaphase AnaphaseTelophase

19. ProphaseEarly ProphaseCentrioles move to the poles of the cellChromosomes appear as long, this threadsNucleus becomes less distinctNuclear membrane is still visibleAsters are formed

20. ProphaseMiddle ProphaseCentrioles begin to organize spindle fibersSister chromatids are formed with the centromere as point of attachment

21. Late ProphaseCentrioles are nearly at the opposite sides of the nucleus

22. Nuclear membrane slowly desintegrates

23. Nucleulus is no longer visible

24. Chromosome move toward the equatorProphaseSpindle fibers attach to the centromere of each chromosomeMetaphaseNuclear membrane has completely disappearedThe centromere of each double-stranded chromosome is attached to a spindle fiber at the equatorCentrioles are at the opposite ends of the polesChromosomes line up at the center forming metaphase plate

25. AnaphaseSister chromatids start to move toward the poles, seemingly being pulled by the thread or fibersEarly AnaphaseSister chromatids separate and begin moving toward opposite poles of the cellAnaphaseA slight cleavage furrow in the cell membrane begins to form in the region of the equatorLate AnaphaseTwo sets of new, single stranded chromosomes start to migrate near their respective poles

26. Cytokinesis beginsTelophaseCentrioles are replicatedCytokineseis is nearly completeSpindle fibers and asters disappearThe cleavage furrow deepens and the cell finally divide onto two partsNew nuclear membrane starts to form in each new cellChromosomes become longer, thinner and less distinctThe nucleus reappears

27. 2ndInterphase: 2 cell stageNuclear membrane are complete in each cells

28. Chromosomes are no longer visible

29. Cytokinesis is complete

30. Two new daughter cells are formed, each with a complete set of materials as the parent cellThe process of MitosisOccur in less than an hour or longer ( some in just 23 minutes)

31. Brain cells do not dived when mature

32. Most frequent/fast in human embryo formationAssessment BreakDefine Mitosis. Why is it important?What are the stages of mitosis?What body cells are involved in mitotic process?When is the process of mitosis faster? Slower?

33. MeiosisA cell division forming reproductive cellsOogenesisSpermatogenesisOccurs in two cycles of division

34. Meiosis Dissected: StagesMeiosis involves two consecutive divisionsIt involves “Crossing Over” or the exchange of DNA traits

35. 1st & 2nd Meiotic DivisionParent Sex CellsChromosomes duplicateCrossing over1st Cell division(2 daughter cells)2 daughter cellsChromosomes pair upChromosomes separate2nd Cell Division) Cell divides into 4 sex cells with haploid chromosomes

36. Mitosis VS Meiosis

37. GametogenesisMeiosis only happens when your body is ready to produce reproductive cellsSpermatgenesis ~ formation of sperm cellsOogenesis ~ formation of egg cells

38. SpermatogenesisThe formation of male gametesAn example of Meiosis

39. OogenesisFormation of Female GameteAn example of Meiosis

40. Spermatogenesis VS Oogenesis

41. Assessment BreakDefine meiosis. How is it different from mitosis?How many cells are formed after the first cell division in meiosis? After the second division?What is gametogenesis?Compare and contrast spermatogenesis and oogenesis.