MEKANISME SEL DAN SIKLUS HIDUP TANAMAN

1. MEKANISME SEL DAN SIKLUS HIDUP TANAMAN

2. MITOSIS • Istilah mitosis : prosesygmenghasilkanduaselanakygidentik. • Mitosis memegangperanandalampertumbuhandanperkembanganorganisme. • Padatanaman mitosis terjadi pd sel-selmeristematis, misalnyakambium, ujung-ujungakar, danujungbatang.

3. Mitosis

4. Prophase In prophase, the cell begins the process of division. 1. The chromosomes condense. The proteins attached to the DNA cause the chromosomes to go from long thin structures to short fat one, which makes them easier to pull apart. 2. The nuclear envelope disappears. The double membrane that surround the nucleus dissolves into a collection of small vesicles, freeing the chromosomes to use the whole cell for division 3. The centrosomes move to opposite poles. During interphase, the pair of centrosomes were together just outside the nucleus. In prophase they separate and move to opposite ends of the cell. 4. The spindle starts to form, growing out of the centrosomes towards the chromosomes.

5. Metaphase Metaphase is a short resting period where the chromosomes are lined up on the equator of the cell, with the centrosomes at opposite ends and the spindle fibers attached to the centromeres. Everything is aligned for the rest of the division process to occur.

6. Anaphase In anaphase, the centromeres divide. At this point, each individual chromosome goes from: 1 chromosome with 2 chromatids to: 2 chromosomes with one chromatid each. Then the spindle fibers contract, and the chromosomes are pulled to opposite poles, towards the centrosomes.

7. Telophase In telophase the cell actually divides. The chromosomes are at the poles of the spindle. The spindle disintegrates The nuclear envelope re-forms around the two sets of chromosomes. The cytoplasm is divided into 2 separate cells, the process of cytokinesis.

8. Cytokinesis The organelles (other than the chromosomes) get divided up into the 2 daughter cells passively: they go with whichever cell they find themselves in. Plant and animal cells divide the cytoplasm in different ways. In plant cells, a new cell wall made of cellulose forms between the 2 new nuclei, about where the chromosomes lined up in metaphase. Cell membranes form along the surfaces of this wall. When the new wall joins with the existing side wall, the 2 cells have become separate. In animal cells, a ring of actin fibers (microfilaments are composed of actin) forms around the cell equator and contacts, pinching the cell in half.

9. Meiosis • Different from somatic cell • Reduces the number of chromosomes in new cells to half the number in the original cell • Produces gametes (sperm and egg cells)

10. Terjadi 4 kejadian penting pd meiosis • Perpasangan kromosom yg homolog (synapsis) • Pertukaran bag kromosom (crossing over) • Distribusi kembali kromosom • Susunan materi genetik mungkin berbeda dg tetua akibat crossing over

11. Gamete Formation • Gametes are sex cells (sperm, eggs) • Arise from germ cells ovaries anther ovary testes

12. Meiosis I Prophase I Metaphase I Anaphase I Telophase I Meiosis II Prophase II Metaphase II Anaphase II Telophase II Stages of Meiosis Mitosis Vs meiosis

13. DNA Replication

14. Meiosis

17. Meiosis I Each homologue in the cell pairs with its partner, then the partners separate

18. Prophase I Metaphase I Anaphase I Telophase I Meiosis I - Stages

19. Prophase I • Each duplicated, condensed chromosome pairs with its homologue (synapsis) • Homologues swap segments (crossing over)

20. Homologous Chromosomes

21. Homologous Chromosomes

22. Synapsis

23. Crossing Over

24. Effect of Crossing Over • After crossing over, each chromosome contains both maternal and parental segments • Creates new allele combinations in offspring

27. Metaphase I • Chromosomes are pushed and pulled into the middle of cell • Sister chromatids of one homologue orient toward one pole, and those of other homologue toward opposite pole

30. Anaphase I • Homologous chromosomes segregate from each other randomly (independent assortment) • Independent assortment results in genetic variation

31. Independent Assortment

32. Telophase I and Cytokinesis • The chromosomes arrive at opposite poles • The cytoplasm divides • There are now two haploid cells • This completes Meiosis I

33. Meiosis II • The two sister chromatids of each duplicated chromosome are separated from each other two chromosomes (unduplicated) one chromosome (duplicated)

34. Prophase II Metaphase II Anaphase II Telophase II Meiosis II - Stages

35. Prophase II • Microtubules attach to the kinetochores of the duplicated chromosomes • Chromosomes move toward the spindle’s equator

36. Metaphase II • All of the duplicated chromosomes are lined up at the spindle equator, midway between the poles

37. Anaphase II • Sister chromatids separate to become independent chromosomes and move to opposite poles

38. Telophase II and Cytokinesis • The chromosomes arrive at opposite ends of the cell • A nuclear envelope forms around each set of chromosomes • The cytoplasm divides • There are now four haploid cells Meiosis Animation I Meiosis Animation II

39. Results of Mitosis and Meiosis • Mitosis • Two diploid cells produced • Each identical to parent • Meiosis • Four haploid cells produced • Differ from parent and one another

40. SIKLUS HIDUP TANAMAN

41. Gametogenesis Tumbuhan • Mikrosporogenesis (pd anther) • Megasporogenesis (pd bunga betina/ovarium)

42. Canna Hibiscus

43. Microsporogenesis

44. Megasporogenesis

45. Megasporogenesis & Megagametogenesis

47. Megasporogenesis & Megagametogenesis

48. Megasporogenesis & Megagametogenesis

49. Terimakasih