Cell reproduction
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LEADING TO MITOSIS AND MEIOSIS
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Cell reproduction
- 1. Leading to Mitosis & Meiosis by Muhammad Iqbal Khan SS Biology Email ID:mikhan1313@yahoo.com
- 4. Mitosis • One type of cell division Cell process in which the nucleus divides to form two nuclei identical to each other, and identical to the original nucleus, in a series of steps (prophase, metaphase, anaphase, and telophase)
- 5. Mitosis allows for growth and replaces worn out or damaged cells.
- 6. Interphase • Period of growth & development • Hereditary information (DNA) copied (replicated / duplicated) • Cells that do not divide (nerves) are always in interphase
- 8. Prophase •DNA begins to shorten & thicken –Now called chromatids / chromosomes •Centromeres form •Nuclear membrane breaks apart •Spindle fibers form
- 10. Metaphase •Chromatids / chromosomes line up •Centromere attaches to spindle fibers
- 12. Anaphase •Centromeres divide •Spindle fibers shorten •Chromatid pairs separate – move to ends of cell •Chromatids are now called –Each ½ of the pair is now called a chromosome
- 14. Telophase •Spindle fibers disappear •Chromosomes uncoil •Nuclear membrane forms •Cell divides (cytokinesis)
- 16. Interphase Prophase Metaphase Anaphase Telophase Interphase http://biology.nebrwesleyan.edu/benham/mitosis/
- 18. Results of Mitosis • Division of nucleus –Nuclei are identical to each other •Same number & type of chromosomes
- 19. Asexual Reproduction A type of reproduction - fission, budding, and regeneration - in which a new organism is produced from one parent and has DNA identical to the parent organism.
- 20. Asexual Reproduction •Offspring produced from one organism •Hereditary information is identical •Mitosis is one form of asexual reproduction
- 22. Sexual Reproduction A type of reproduction in which two sex cells, usually an egg and a sperm, join to form a zygote, which will develop into a new organism with a unique identity.
- 23. Sexual reproduction results in a great variety, or diversity, of offspring.
- 24. Meiosis • The nucleus divides twice – Meiosis I – Meiosis II
- 26. Interphase • DNA is duplicated
- 27. Prophase I • DNA shorten & thicken – Forms chromatids / chromosomes
- 29. Metaphase I •Copied chromatids / chromosomes line up in middle of cell •Centromeres attach to spindle fibers
- 31. Anaphase I •Chromatid pairs are pulled apart –They DO NOT separate •Move to ends of cell
- 33. Telophase I •Cell divides •No further replication of hereditary material
- 35. There are now two cells. Both cells have full sets of genetic material (chromosomes)
- 36. Prophase II •Similar to mitosis –Starts with TWO cells instead of one •Spindle fibers appear
- 38. Metaphase II •Duplicated chromatid / chromosomes line up in middle of cell •Spindle fibers attach to centromeres
- 40. Anaphase II •Centromere divides –Chromatids separate & move to ends of cell •Chromatids are now individual chromosomes
- 42. Telophase II •Spindle fibers disappear •Nuclear membranes form at each end of cell •Cells divide –Results in 4 cells •Each with ½ the original number of chromosomes
- 45. In summary: Meiosis • Two cells form during meiosis I • In meiosis II, both of these cells form two cells • The two divisions of the nucleus result in four sex cells (gametes) • Each has one-half the number of chromosomes in its nucleus that was in the original nucleus