Mitosis: “nuclear division” All living things follow a similar path from beginning to end.

8.6 Mitosis Stages In cell cyle, we’ve finished DNA synthesis In cell cyle, we’ve finished DNA synthesis The cell grows and prepares for mitosis in G2 The cell grows and prepares for mitosis in G2

Mitosis Now we have enough DNA for two daughter cells Now we have enough DNA for two daughter cells The cells must equally divide the DNA so each daughter cell gets their own set. The cells must equally divide the DNA so each daughter cell gets their own set. Mitosis: the process of sorting and dsitributing chromosomes Mitosis: the process of sorting and dsitributing chromosomes

Chromosomes Each old strand paired with a new strand Each old strand paired with a new strand Called “sister chromatids” Called “sister chromatids” “sister chromatids” connected by “centromeres” “sister chromatids” connected by “centromeres” –Narrow point with proteins binding them together Sister Chromatids

Chromosomes Each old strand paired with a new strand Each old strand paired with a new strand Called “sister chromatids” Called “sister chromatids” “sister chromatids” connected by “centromeres” “sister chromatids” connected by “centromeres” –Narrow point with proteins binding them together Sister Chromatids

Chromosomes Each old strand paired with a new strand Each old strand paired with a new strand Called “sister chromatids” Called “sister chromatids” “sister chromatids” connected by “centromeres” “sister chromatids” connected by “centromeres” –Narrow point with proteins binding them together Sister Chromatids

Mitosis Actually a continuous process Actually a continuous process Like a film of someone doing a back flip Like a film of someone doing a back flip To make it easier to understand: break it up into phases To make it easier to understand: break it up into phases –1. Interphase –2. Prophase –3. Pro-metaphase or Late Prophase –4. Metaphase –5. Anaphase –6. Telophase –7. Cytokinesis

Interphase “time between cell divisions” “time between cell divisions” –Prepares for mitosis Chromosomes not visible Chromosomes not visible –Nucleolus easy to spot “little nucleus” “little nucleus” Round structure in nucleus Round structure in nucleus Makes RNA Makes RNA Pair of centrioles may be present Pair of centrioles may be present Important later on Important later on

Prophase or Early Prophase Chromatin begins to condense Chromatin begins to condense –Chromosomes become visible Nucleolus disappears Nucleolus disappears Centrioles move to opposite ends Centrioles move to opposite ends Fibers begin to extend from centromeres Fibers begin to extend from centromeres

Pro-metaphase A.k.a. “Late Prophase” A.k.a. “Late Prophase” Not even mentioned in your book Not even mentioned in your book Nuclear membrane dissolves Nuclear membrane dissolves Proteins attach to centromeres Proteins attach to centromeres –Forms kinetochores This forms the mitotic spindle (fibers= microtubules) This forms the mitotic spindle (fibers= microtubules)

Metaphase Spindle fibers line up chromosomes down middle Spindle fibers line up chromosomes down middle Chromosomes line up on “metaphase plate” Chromosomes line up on “metaphase plate”

Anaphase Paired chromosomes separate at centromere Paired chromosomes separate at centromere –Protein binding them together breaks down Spindle microtubules start pulling chromosomes to opposite ends of cell towards centrioles

Telophase Chromosomes arrive at opposite poles of cell Chromosomes arrive at opposite poles of cell New nuclear membranes form around daughter nuclei New nuclear membranes form around daughter nuclei –Keep separated DNA from mixing again Chromosomes start to disperse Chromosomes start to disperse –Chromosomes no longer visible

Cytokinesis DNA is divided equally DNA is divided equally Rest of cell divides into two identical cells Rest of cell divides into two identical cells –Can begin during early stages Animal cells: “actin” constricts around center of cell til it pinches it in two Animal cells: “actin” constricts around center of cell til it pinches it in two Plant cells: A cell plate is synthesized down the center Plant cells: A cell plate is synthesized down the center –Like two girls forced to share a room build a wall down the middle of room –Video1 video2 Video1videoVideo1video

END END Mitosis is pau Mitosis is pau Parent cell has finished cell cycle Parent cell has finished cell cycle Result: 2 daughter cells Result: 2 daughter cells –Daughter cells begin their own cycle –Enter G1