M Phase – Cell Division Divided into two parts Mitosis Cytokinesis division of the cell’s nucleus Cytokinesis division of the cell’s cytoplasm

M Phase – Cell Division Chromatin Chromosome Chromatids all of the chromosomes in the nucleus Chromosome a single piece of DNA in the nucleus Chromatids two identical “sister” replicated chromosomes, held together by a centromere

Chromosomes Individual Chromosomes Chromatin

Chromosome Visibility Chromosomes become visible during cell division as they condense (coil) to become more manageable during separation.

Please flip your notes to the opposite side of the page.

Chromosomes a One chromosome (unduplicated) centromere one chromatid two sister chromatids one chromatid b One chromosome (duplicated)

Flip your page again. Attempt to label each blank on your notes. 1. _____________________ 5. _________________ 2. _________________ 3. _____________________ 4. _____________________

Now correct each label on your notes. 1. chromosome 5. centromere 2. sister chromatids 4. chromatid 3. chromatid

Maintaining Chromosome Number When cells divide, each cell duplicates an entire copy of its chromatin. When the cell divides, each “daughter cell” receives one complete copy of the chromatin. This allows each cell to have the same number of total chromosomes.

Maintaining Chromosome Number chromosome (unduplicated) in cell Maintaining Chromosome Number same chromosome (duplicated) prior to mitosis mitosis & cytokinesis chromosome (unduplicated) in daughter cell at interphase

Maintaining Chromosome Number The two new daughter cells will be genetic twins, and they will genetically be identical to the cell they came from.

Mitosis Mitosis occurs in 4 phases: Prophase Metaphase Anaphase Telophase

Mitosis Prophase

Mitosis Prophase Chromatin condenses into individual chromosomes Nuclear envelope breaks down Centrioles separate Centrioles – specialized structures in animal cells that help pull apart duplicated chromosomes

Mitosis Metaphase

Mitosis Metaphase Chromosomes line up across the center of the cell Each chromosome is connected to a spindle fiber at its centromere Spindle fibers –microtubules fibers that move chromosomes in animals, centrioles pull on the spindle fibers in plants, fibers attach directly to the cell wall

Mitosis Anaphase

Mitosis Anaphase Sister chromatids separate into individual chromosomes and are moved apart As the chromatids are no longer connected, the centromeres that connected them no longer exist.

Mitosis Telophase

Mitosis Telophase Chromosomes gather at opposite ends of the cell and lose their distinct shapes Two new nuclear envelopes form Spindle dissolves Cells begin to separate in preparation for cytokinesis

What is visible in mitosis that is unable to be seen in interphase?

Cytokinesis the cytoplasm of the cell is divided in half the cell membrane grows to surround each new daughter cell

Mitosis & Cytokinesis 1. Interphase 2. Prophase 3. Metaphase 4. Early Anaphase 5. Late Anaphase 6. Telophase 7. Cytokinesis 8. Interphase

Mitosis & Cytokinesis Animation

Cytokinesis in Plants the cell is divided in half by a cell plate cell plate – a newly formed cell wall

Mitosis in Animals vs. Plant Cells Differently shaped cells Plants Square-ish Animals Round-ish Differences in cytokinesis No cell wall/cell plate in animal cells

Summary Why is mitosis important? In other words, why is it important that a cell can copy its DNA (during Synthesis) and divide its DNA (during Cell Division)?