Objectives 1) Name three parts of the cell cycle. 2) Name four major parts of mitosis. 3) Identify important parts of a dividing cell. 4) Discuss important similarities and differences between mitosis and meiosis.

The cell cycle has three major parts: 1. Interphase 2. Mitosis (Karyokinesis) (Mitosis has four major sub-parts) 1) Prophase 2) Metaphase 3) Anaphase 4) Telophase 3. Cytokinesis

Interphase Characterized by: 1.Intact nuclear envelope 2.Visible nucleolus 3.Although you can’t tell it, the cell’s DNA and other cell components are undergoing a process called replication (duplication process); chromosomes become double- stranded. 4. Three sub-phases: G 1, S, and G 2 Nuclear envelope Nucleolus

Prophase Characterized by: 1.Disappearing nuclear envelope and nucleolus 2.Chromosomes (46* in each human cell) coil and condense 3.Spindle fibers (microtubules) form and chromosomes become attached by way of centromeres 4.Newly formed centrioles move to opposite ends of the cell Condensed chromosomes (chromatin fibers) *23 pairs of chromosomes Mitosis = Karyokinesis

Metaphase Characterized by: 1.Chromosomes align across the “equator” or metaphase plate 2.Centrioles stop at opposite ends of the cell 3.Spindle apparatus is fully formed Metaphase plate Centrioles Spindle apparatus Mitosis = Karyokinesis

Anaphase Characterized by: 1.Spindle fibers (microtubules) shorten and separate the chromosomes at the metaphase plate 2.In the human cell, 46 single- stranded chromosomes move in opposite directions toward each pole Centrioles Shortening microtubules (spindle fibers) Mitosis = Karyokinesis

Can you name structures in the dividing cell? single-stranded chromosome centromere centrioles spindle fiber (microtubule)

Telophase Characterized by: 1.Cleavage furrow forms 2.Nuclear envelopes begin to form around two daughter nuclei 3.Chromosomes decondense 4.Spindle disappears cleavage furrow daughter nuclei Mitosis = Karyokinesis Cytokinesis (Division of cytoplasm and contents into two cells)

This figure represents an overview of the cell cycle.

This figure represents an overview of meiosis (human male)

This figure represents an overview of meiosis (human female)

MITOSIS MEIOSIS All chromosomes align at metaphase plate Homologous pairs of chromosomes align One set of divisions: P – M – A – T Two sets of divisions: PI - MI – AI – TI PII – MII – AII – TII 2 daughter cells4 daughter cells (male) 1 cell and polar bodies (female) daughter cells diploid (2n; same as original cell) daughter cells haploid (n; half chromosomes as original cell) Growth and repairFormation of sex cells Similarities and Differences