Mitosis

1. Mitosis • Purpose: occurs in somatic (body) cells for growth and repair of tissue (ex. Growing, or healing an injury). Occurs in both plants and animals: asexual reproduction, (starting a new plant from a stem/leaf of another one)

2. Method: mitosis involves one duplication of nuclear material, and one division of the cell. Chromosome number is maintained (diploid  diploid (normal chromosome #). • Daughter cells are identical to each other and to the parent cell.

3. The cellular life cycle

4. Cell Cycle: • Interphase – mostly the active growth and metabolism of the cell, but at the end of interphase, DNA (found in chromosomes) duplicates (makes a copy of itself) • During interphase, chromosomes are referred to as chromatin – a loosely scattered arrangement of chromosomes

5. Mitotic Phase • Period of cell division • Shortest stage in the cell cycle

7. Chromosomes Vs. Chromatin • DNA exists in Chromatin form in the nucleus. • The chromatin condenses to form Chromosomesduring cell division

9. INTERPHASE: The normal growth and development stage of cells • During this stage cellular activities proceed normally • There is no DNA replication • Cell produces proteins through protein synthesis • Cells usually increase in size and mass • Chromosomes are not readily visible and are intertwined in the nucleus

10. This is known as the “G1 stage” of the cellular cycle. The cell spends the majority of its life in this stage. • The cell then enters the “S” or Synthesis stage. During this stage of Interphase DNA replication occurs and the chromosomes make identical copies of themselves. • The “G2 stage” is a short period of growth and other preparations necessary for mitosis.

11. Interphase in an animal cell

15. PROPHASE: At the end of Interphase the chromosomes replicate themselves. This signals the start of prophase • During prophase the centrioles migrate to opposite poles of the cell • The nuclear membrane breaks down and dissolves • The chromosomes shorten & thicken

17. Prophase in a plant cell

18. Prophase in an animal cell

19. At this point the two replicas of the parent chromosomes are called chromatids • The two chromatids are joined together in a region known as the centromere • As prophase continues some of the cells cytoskeleton (made up of microfilaments) form the spindle fibers • By the end of prophase an entire network of microfilaments has formed and is attached to the chromatids at the centromere • The cell now enters METAPHASE

20. Metaphase begins as the chromatids begin to move towards the equator of the cell • When all the chromatids have reached the center of the cell AND begin to separate ANAPHASE begins

23. Metaphase in an animal cell

24. Metaphase in a plant cell

25. What differences can you describe between the 1st Meiotic metaphase and the metaphase in mitosis? • What differences can you describe between the 2nd Meiotic metaphase and the metaphase in mitosis?

26. Anaphase begins with the separation of chromatid pairs • Once separated each chromatid is called a chromosomes • By late anaphase an equal number of chromosomes has reached each pole • The cell membrane begins to change shape getting thinner in the middle

28. Anaphase in an animal cell

29. Anaphase in a plant cell

30. Telophase: during early telophase the chromosomes uncoil • The fragments of the nuclear membrane begin to reassemble around the chromosomes • The nucleolus reappears • The cell membrane, and cell plate in plant cells, begins to form in the space between the two new nuclei.

33. Telophase in an animal cell

34. Telophase in a plant cell

38. The two daughter cells separate by a process called cytokinesis • The cell membrane returns to normal and the new daughter cells enter Interphase • And the cycle continues…..

41. Vocab Words