You started as a cell smaller than a period at the end of a sentence… You started as a cell smaller than a period at the end of a sentence… . And now look at you! How did you get from there to here?

Cell Division

Preparing for Cell Division Interphase prepares the cell for cell division. DNA is replicated DNA is in the form of chromatin & doesn’t condense into chromosomes until mitosis begins.

Somatic Cells are Diploid (2n) Diploid (2n) cells have 2 copies of every chromosome. Humans have 23 pairs of homologous chromosomes, 23 from mom & 23 from dad. Chromosome number must be maintained! Mitosis results in more diploid cells. Daughter cells are genetically identical to the parent cell.

Why do cells divide again? Reproduction Growth & Development Repair & Replacement

The Phases of Mitosis & Cytokinesis

Overview of Cell Division (I.P.M.A.T.)

Prophase Longest phase in mitosis (takes 50-60% of total time mitosis requires) Chromosomes become visible, because they are condensed.

Prophase 2. Centrioles move to opposite ends of the cell. 3. Spindle fibers form between centrioles. 4. The nucleolus disappears & the nuclear envelope breaks down.

Metaphase Chromosomes line up in the center of the cell. Spindle fibers attach to the centromere of each chromosome.

Anaphase Sister chromatids separate from each other & are pulled to opposite ends of the cell. Anaphase ends when the chromosomes stop moving.

This is the end of mitosis, but NOT the end of cell division. Telophase Chromosomes look like threads (chromatin) again. A nuclear envelope forms around each cluster of chromosomes. Spindle breaks apart This is the end of mitosis, but NOT the end of cell division.

Mitosis End Result In eukaryotes, the nucleus is divided into 2 separate nuclei. Mitosis conserves the number of chromosomes & equally allocates the replicated chromosomes into each of the daughter nuclei.

Cytokinesis – NOT part of mitosis! Cell division is not complete until the cytoplasm divides. Remember, the M Phase includes: Mitosis Cytokinesis

Cytokinesis In plants, a cell plate forms between the 2 daughter nuclei. The cell plate develops into a cell membrane & cell wall.

Cytokinesis In animal cells, the cell membrane is drawn inward until the cytoplasm is pinched into 2 equal parts. Each part has a nucleus & organelles.

Prophase

Metaphase

Anaphase

Telophase

Cytokinesis

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