Objectives Name three parts of the cell cycle. Name four major parts of mitosis. Identify important parts of a dividing cell.

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: Intact nuclear envelope Visible nucleolus 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: G1, S, and G2 Nuclear envelope Nucleolus

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

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

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

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

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

This figure represents an overview of the cell cycle.