1. Sara, Ranyah, Kara and Erica
The Mitotic Phase
Sara, Ranyah, Kara and Erica

2. Let’s start off with a video..

3. Cell cycle overview

4. G1 Phase “First Gap” Cell grows 5-6 hours Part of interphase
Varies by cell type

5. S Phase “Synthesis” Cell still grows
Chromosomes duplicate in this phase only
10-12 hours
Half the cycle

6. G2 Phase “Second Gap” Grows still Prepares for cell division 4-6 hours
Last part of interphase

7. M Phase “Division” <1 hour Divides!
Alternates with interphase(growth period)
Daughter chromosomes → Daughter nuclei
Mitosis
Cytokinesis divide
Cytoplasm
Produces 2 daughter cells

8. Phase 1: Interphase Nuclear envelope encloses the nucleus
Nucleus contains one or more nuclei
Two centrosomes have formed from duplication of single centrosome

9. Phase 2: Prophase Chromatin fibers become more tightly coiled
Nucleoli disappear
Each duplicated chromosome appears as two identical sister chromatids which join at their centromeres

10. Phase 2: Prophase continued
Mitotic spindle (the shape name) beings to form and is composed of the centrosomes and microtubules that extend from them
Asters: radial arrays of shorter microtubules that extend from the centrosomes
Centrosomes move away from each other

11. phase 3: Prometaphase Nuclear envelope fragments
Microtubules from centrosomes can now invade the nuclear area
Chromosomes become more condensed
Each chromatid now has a special protein called a kinetochore
Kinetochore: a structure of proteins associated with specific sections of chromosomal DNA at each centromere

12. Phase 3: prometaphase continued
Some microtubules attach to kinetochore causing chromosomes to jerk back and forth
Nonkinetochore microtubules interact with others at the opposite end of the spindle

13. phase 4: MEtaphase Centrosomes are now at opposite poles of the cell
Chromosomes meet at the metaphase plate
Metaphase plate: A plane that is equal distance between the spindle’s two poles
Chromosomes’ centromeres lie at the plate

14. phase 4: MEtaphase continued
For each chromosome, the kinetochores of sister chromatids are attached to kinetochore microtubules coming from opposite poles
Centromere: region containing specific DNA sequences where the chromatid is attached most closely to its sister chromatic

15. phase 5: Anaphase Anaphase is the shortest stage
Cohesins holding together the sister chromatids are separated by proteins
Sister chromatids become daughter chromosomes and move toward opposite ends of cell
The kinetochore microtubules attached to centrosomes shorten
Cell elongates as nonkinetochore microtubules lengthen
By the end of anaphase, both sides of the cell have equal numbers of chromosomes

16. phase 6: TELOPHASE Two daughter nuclei form in the cell
Nuclear envelopes arise from fragments of the parents cell’s nuclear envelope
Nucleoli reappear
Chromosomes less condensed spindle microtubules are depolymerized
Mitosis, which the division of one nucleus into two genetically identical nuclei, is now complete

17. CYTOKINESIS
Division of the cytoplasm is usually underway by late telophase, so the two daughter cells appear shortly after the end of mitosis
In animal cells cytokinesis involves the formation of a cleavage furrow, which pinches the cell in two.

18. Cytokinesis in an animal cell
Cytokinesis in animal cells occurs by a process known as cleavage. The first sign of cleavage is an appearance of a cleavage furrow. A cleavage furrow is a shallow groove in the cell surface near the old metaphase plate. On the cytoplasmic side of the furrow is a contractile ring of actin microfilaments. The actin microfilaments interact with the protein myosin, causing the ring to contract. The furrow deepens until the parent cell is pinched in two, producing two completely separated cells.

19. Cytokinesis in a plant cell
Cytokinesis is different in the plant cell due to the plant cell having a cell wall. The membrane cannot contract to pinch off the cell, therefore there is no cleavage furrow. During telophase vesicles from the Golgi Apparatus move along microtubules to the middle of the cell, where they combine producing a cell plate. Cell wall materials carried in the vesicles collect in the cell plate as it grows. The cell plate enlarges until its surrounding membrane fuses with the plasma membrane along the perimeter of the cell. Two daughter cells are formed and a new cell wall forms from the contents of the cell plate.

20. Cytokinesis Overview Animal cells: Cleavage furrow
Plant cells: Cell plate

21. Binary fusion
Binary fusion “Division in half” - the process in which the cell grows to roughly double its size and then divides to form two cells.
The asexual reproduction of a single-celled eukaryote.
Origin of replication - specific place on the chromosome where the process of cell division is initiated.

22. Prokaryotes vs Eukaryotes
Mode of reproduction
Binary fission
Requires mitosis
Number of chromosomes
Varies based on the species
Shape of the bacterial chromosome
Linear
Prokaryotes
Mode of reproduction
Binary fission
Doesn’t require mitosis
Number of chromosomes 1
Shape of the bacterial chromosome
Circular
Examples of the number of chromosomes in eukaryotic organisms:
Humans have 46 chromosomes
Dogs have 78 chromosomes
Earthworms have 36 chromosomes