5.2 Mitosis and Cytokinesis

KEY CONCEPT Cells divide during mitosis and cytokinesis.

5.2 Mitosis and Cytokinesis

• One long continuous thread of DNA coiled around histones (proteins) is called chromatin.

• One half of a duplicated chromosome is a chromatid.

• Sister chromatids are held together at the centromere.

• Telomeres protect DNA and do not include genes.

Condensed, duplicated chromosome

chromatid

centromere

telomere

5.2 Mitosis and Cytokinesis

Chromosomes condense at the start of mitosis.

• DNA wraps around proteins (histones) that condense it.

DNA doublehelix

DNA andhistones

Chromatin SupercoiledDNA

5.2 Mitosis and Cytokinesis

Parent cell

centrioles

spindle fibers

centrosome

nucleus withDNA

• 1.Interphase prepares the cell to divide.

• DNA is duplicated.

B. Mitotic Phase- Mitosis and cytokinesis produce two genetically identical daughter cells.

5.2 Mitosis and Cytokinesis

Cell structures and mitosis

• Centrosomes-organelle that is the main microtubule organizing center.

• Aster-cellular star shaped structure that forms around the centrosome-made of microtubules

• Equator-mid section of the dividing cell• Cleavage furrow - indentation that begins the formation of

the new cell membrane• Cell plate- the new cell wall• Kinetorchore fibers- attachment points on the centromere

where the chromosomes are held together to make an X• Spindle- fibers that separate the chromosomes• Microtubules-hollow, protein fibers and rods.• Cytokinesis-division of the cytoplasm results two

daughter cells.

5.2 Mitosis and Cytokinesis

2.During prophase, chromosomes condense, nuclear membrane, nucleus, and nucleolus disappear, spindle fibers form, centrioles make spindle fibers

5.2 Mitosis and Cytokinesis

– 3.During metaphase- spindle fibers randomly align sister chromatids in the middle of the cell (equator)

5.2 Mitosis and Cytokinesis

– 4.During anaphase- spindle fibers retract and pull the sister chromatids opposite sides of the cell (poles)

5.2 Mitosis and Cytokinesis

– 5.During telophase- chromosomes uncoil, nuclear membrane reforms, nucleolus reforms.

5.2 Mitosis and Cytokinesis

• 6.Cytokinesis-division of the cytoplasm

– In animal cells, the membrane pinches closed at a point called cleavage furrow.

– In plant cells-vacuoles join together and form a cell plate.

Result-2 identical daughter cells with identical copies of genetic material-DNA

5.2 Mitosis and Cytokinesis

5.2 Mitosis and Cytokinesis

5.2 Mitosis and Cytokinesis

5.2 Mitosis and Cytokinesis

5.2 Mitosis and Cytokinesis