12.2: Mitosis and Interphase of Animals Justine & Nicko

Interphase G1- Regular cell functions and the cell grows S- Chromosomes copied (but cell continues to grow) G2- the cell prepares to divide and continues to grow M-cell divides

Mitosis Phases G2 of interphase Prophase Prometaphase Metaphase Anaphase Telophase Cytokinesis

Interphase Nucleus is enclosed DNA is still in strands (chromatin) Centrosomes formed

Prophase Chromatin fibers more tightly coiled Nucleoli disappear Chromatid forms chromosomes with two sister chromatid Mitotic spindle begins to form Composed of centrosomes and their microtubules Centrosomes move away from each other

Prometaphase Chromosomes become more condense Kinetochore forms Kinetochore microtubules attach to kinetacore

Metaphase Centrosomes at opposite poles of cell Chromosomes meet at metaphase plate Equal distance from two poles Kinetochores of the sister chromatids attached to kinetochore microtubules from opposite poles

Anaphase Sister chromatid pulled apart by centromere Creates 2 daughter chromosomes Kinetochore microtubules shorten This pulls the daughter chromosomes toward the two opposite poles Short in time Each pole ends up with the same amount of chromosomes

Telophase Two daughter nuclei form Nuclear envelopes form from fragments of parent cell’s nuclear envelope Nucleoli reappear Chromosomes less condensed Remaining spindle microtubules depolymerized Mitosis complete (division of one nucleus → two identical nuclei)

Cytokinesis Two daughter cells appear shortly after mitosis Formation of cleavage furrow (pinches cell in two) Animal cell: Plant cell:

Binary Fission Division in half How prokaryotes replicate Cell grows to twice its size and then splits into two daughter cells Origin of replication: place on the chromosome where the DNA of the bacterial chromosome starts to replicate

Prokaryotic vs. Eukaryotic Cells Mode of reproduction Pro: Binary Fission Eu: Mitosis Number of chromosomes: Pro: Less Eu: Much more Shape of chromosomes: Pro: Circular Eu: Linear