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- 2. Mitosis Mitosis • The form of cell division cell division by which a eukaryotic somatic cell somatic cell duplicates. • • Mitosis Mitosis is asexual reproduction. asexual reproduction. • • Cell division Cell division is the continuation of life based on the reproduction of cells.
- 4. Somatic Reproduction Somatic Reproduction • Most eukaryotic cells reproduce asexually by mitosis mitosis. • • Somatic cells Somatic cells are all body cells body cells (like nerve, (like nerve, liver, etc...) liver, etc...) except sperm and ova (egg). • All Somatic cells have the same number of chromosomes chromosomes.
- 5. Cell Cycle Cell Cycle • The dividing dividing and non non- -dividing dividing stages in the life of a cell. • Phases: 1. 1. Interphase Interphase: growth and DNA replication 2. 2. Prophase Prophase 3. 3. Metaphase Metaphase 4. 4. Anaphase Anaphase 5. 5. Telophase Telophase Mitotic division Mitotic division
- 6. Cell Cycle Cell Cycle Mitosis -prophase -metaphase -anaphase -telophase G1 G2 S phase interphase
- 7. Interphase Interphase • Comprises about 90% 90% of the cell cycle cell cycle. • • Cellular growth Cellular growth: a. protein synthesis protein synthesis b. metabolic activities metabolic activities c. DNA DNA synthesis synthesis • Made up of three phases three phases: 1. G 1. G1 1 phase phase 2. S phase 2. S phase 3. G 3. G2 2 phase phase
- 8. Interphase Interphase 1. G 1. G1 1 (gap) phase: (gap) phase: a. protein synthesis and metabolic activities. b. most cell are arrested in this phase most cell are arrested in this phase. 2. S phase: 2. S phase: a. DNA DNA replication replication takes place. 3. G 3. G2 2 (gap) phase: (gap) phase: a. Cellular growth and preparation for M phase M phase.
- 9. Interphase Interphase • • Nucleus Nucleus and nucleolus nucleolus visible. Nuclear membrane nucleolus cell membrane chromatin
- 10. Question: Question: • • What is a What is a chromosome chromosome? ?
- 11. Answer: Answer: • A chromosome chromosome is made up of a DNA DNA - histone protein histone protein complex called chromatin chromatin. • • Chromatin Chromatin is a long, thin fiber that is folded and coiled to form chromosomes chromosomes. DNA double helix Histone proteins chromosome
- 12. Question: Question: • • What is a replicated What is a replicated chromosome chromosome? ?
- 13. Answer: Answer: • A replicated chromosome chromosome consist of two strands of identical chromosomal material called chromatids chromatids (sister chromatids sister chromatids). chromatid chromatid S phase: chromosomes replicate chromosome chromosome centromere
- 14. Mitotic Phase Mitotic Phase • • Mitosis (karyokinesis) Mitosis (karyokinesis) a. nuclear nuclear division of genetic material genetic material. b. prophase b. prophase- -metaphase metaphase- -anaphase anaphase- -telophase telophase • • Cytokinesis Cytokinesis a. a. cytoplasmic division cytoplasmic division. b. Indicator of telophase.
- 15. Prophase Prophase • • Longest phase Longest phase • Nucleolus disappears • Chromatin material condenses into chromosomes chromosomes, consisting of two sister sister chromatids chromatids.
- 16. Prophase Prophase • • Centrioles Centrioles move apart (not found in plants). • • Spindle fibers Spindle fibers ( (microtubules microtubules) ) form and attach from centrioles centrioles to centromeres by centromeres by kinetochores. kinetochores. • Nuclear envelope fragments and disappears.
- 17. Prophase Prophase late prophase late prophase, , promethaphase promethaphase early prophase early prophase centrioles centromere nuclear envelope disappearing
- 18. Question: Question: • • What attaches the What attaches the spindle fibers spindle fibers to to the the centromeres centromeres? ?
- 19. Answer: Answer: Kinetochores Kinetochores sister sister chromatid chromatid sister sister chromatid chromatid centromere centromere spindle fiber spindle fiber kinetochores kinetochores centriole aster fibers
- 20. Metaphase Metaphase • Shortest phase • • Centrioles Centrioles are at opposite ends of the cell and attached with aster fibers aster fibers. • • Chromosomes Chromosomes move to the metaphase metaphase plate plate (equatorial plate equatorial plate - center of cell).
- 22. Metaphase Metaphase • Top of spiralisation, chromatin is in max. of condensation • Chromosomes collect at equatorial plate • At the end of metaphase centromere start dissapears
- 23. Anaphase Anaphase • • Centromeres Centromeres uncouple and spindle fibers spindle fibers shorten. • • Sister chromatids Sister chromatids separate and move apart. • After separation, chromatids chromatids are now considered chromosomes chromosomes.
- 24. Anaphase Anaphase • During this phase, the cell contains twice the normal number of chromosomes chromosomes. • Cell begins to elongate elongate. • At the end, there are equal numbers of chromosomes chromosomes at the poles.
- 25. Anaphase Anaphase No longer sister chromatids sister chromatids, now chromosomes chromosomes centrioles spindle fibers aster fibers
- 27. Telophase Telophase • Nuclear membrane reappears. • • Chromosomes Chromosomes uncoil- despirelation and decondesation • In the end, two genetically identical nuclei (karyokinesis karyokinesis completed) are present.
- 28. Telophase Telophase cleavage furrow (cytokinesis) nuclear membrane reforming nucleolus reappears
- 30. Cytokinesis Cytokinesis • • Cytoplasmic division Cytoplasmic division • • Cell plate Cell plate complete in plants plants • In the end, two separate daughter cells produced with single nucleus. cell plate