Mitosis - Cell division

http://www.youtube.com/watch?v=VGV3fv-uZYI

• Living organisms have life cycles.

• Life cycles begin with organism’s formation, followed by growth and development and end in death.

• Individual cells have life cycles.

• Some cells constantly complete the cycle, others take 16-20 hours or longer.

• Cell cycle is broken down into sections

Interphase

• The longest part of a cell’s life cycle• Several major things occur during

Interphase; – The cell grows, develops. – Organelles are duplicated.– The DNA is copied (chromosomes

duplicated)

• The cell prepares for cell division.• Interphase is NOT part of mitosis.

Interphase

• In Interphase, chromatids are duplicated.

• When the nucleus is ready to divide, each duplicated chromosome coils into two thickened strands called chromatids.

Mitosis• Mitosis: process

in which the nucleus divides to form two identical nuclei.

• Steps of Mitosis: Prophase, Metaphase, Anaphase, and Telophase. (PMAT)

Prophase (Prepare)

• First step of mitosis• Chromatids are fully visible under a microscope• Nucleolus and nuclear membrane disintegrate• Two organelles called centrioles move to

opposite ends in the cell.• Between the centrioles, (only in animal cells)

thin threadlike structures called spindle fibers begin to stretch across the cell.

Metaphase (Middle)

• The chromosomes line up across the midline of the cell.

• The centromere of each chromosome becomes attached to the spindle fibers.

Anaphase (Apart)

• The centromere, in the center of each pair of chromatids, splits in half.

• The spindle fibers shorten, pulling the pair of chromatids apart.

• Each pair of chromatids separate, and move to opposite ends of the cell.

Telophase (Two nuclei form)

• Spindle fibers disappear.

• Nuclear membrane reappears.

• Chromosomes begin to uncoil and a new nucleus forms.

Cytokinesis

• Division of the cytoplasm

• In animal cells – the cell membrane pinches in the middle.

• In plant cells – a cell plate forms followed by the formation of new cell walls .

• Then cells enter into Interphase to repeat the cell cycle again.

Cytokinesis

Animal Cell

Plant Cell

Why doesn’t a plant cell pinch in at the sides like an animal cell?

Onion Root Tip Cells

Results of Mitosis• Mitosis is the division of a nucleus.

• The process produces two new nuclei that are identical to each other and to the original nucleus.

Why does mitosis happen?

• Mitosis allows for: – Growth – Replacement of worn out or damaged cells– In some organisms, it is used to produce new

organisms

Asexual Reproduction

• A new organism is produced from one organism.

• The new organism has exactly the same hereditary material as the parent organism.

Asexual Reproduction in Plants

Asexual Reproduction in Animals

Budding and Regenerationhttp://www.youtube.com/watch?v=489CSop00sY

http://www.youtube.com/watch?v=f7cXeWxxfD4

Prokaryotic organisms cannot undergo mitosis (they have no

nucleus) They reproduce asexually using fission

http://www.youtube.com/watch?v=VGV3fv-uZYI

What are the stages?

1. Interphase

2. Prophase

3. Metaphase

4. Anaphase

5. Telophase

6. Cytokinesis

Identify each stage of the cell cycle(no cytokinesis stage)

Answers

1. Metaphase2. Prophase3. Telophase4. Interphase5. Interphase6. Interphase7. Anaphase8. Interphase9. Anaphase10. Interphase

11. Metaphase12. Telophase13. Interphase14. Prophase15. Interphase16. Interphase17. Metaphase18. Interphase

Which stage is the longest: Interphase