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 itself Reproduction is a Life Process more of the same unit is formed not essential for survival is a need to perpetuate species

3. Chapter Objectives At 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 Terms DNA Chromatids Histones Helix Chromosome Chromatin Nucleosomes

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

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

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

11. Cells of the Human Body Somatic Cells Diploid number (2N) or complete set of (46) Chromosomes Ex. Skin Cells Lung Cells etc. Reproductive Cells Haploid number (N) or half (23) number of chromosomes. Ex. Sperm Cell Egg Cell

12. Assessment Break Explain the limits of Cell Growth. Why do cells divide? Distinguish between Somatic and Germ Cells Haploid and Diploid

13. MITOSIS During 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’ Interphase G1 ~ 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 Division Karyokinesis Splitting of the nucleus Inside nuclear events of the cell Cytokinesis Cytoplasmic Division Outside nuclear events of the cell

17. Mitosis

18. Phases of Mitosis Mitosis begins after Interphase Stages/Phases Prophase Metaphase Anaphase Telophase

19. Prophase Early Prophase Centrioles move to the poles of the cell Chromosomes appear as long, this threads Nucleus becomes less distinct Nuclear membrane is still visible Asters are formed

20. Prophase Middle Prophase Centrioles begin to organize spindle fibers Sister chromatids are formed with the centromere as point of attachment

22. Nuclear membrane slowly desintegrates

23. Nucleulus is no longer visible

28. Chromosomes are no longer visible

29. Cytokinesis is complete

31. Brain cells do not dived when mature

33. Meiosis A cell division forming reproductive cells Oogenesis Spermatogenesis Occurs in two cycles of division

34. Meiosis Dissected: Stages Meiosis involves two consecutive divisions It involves “Crossing Over” or the exchange of DNA traits

35. 1st & 2nd Meiotic Division Parent Sex Cells Chromosomes duplicate Crossing over 1st Cell division (2 daughter cells) 2 daughter cells Chromosomes pair up Chromosomes separate 2nd Cell Division) Cell divides into 4 sex cells with haploid chromosomes

36. Mitosis VS Meiosis

38. Spermatogenesis The formation of male gametes An example of Meiosis

39. Oogenesis Formation of Female Gamete An example of Meiosis

40. Spermatogenesis VS Oogenesis

41. Assessment Break Define 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.