Mitosis: “nuclear Mitosis: “nuclear division”division”

All living things follow a All living things follow a similar path from beginning to similar path from beginning to end.end.

8.6 Mitosis Stages8.6 Mitosis Stages

In cell cyle, In cell cyle, we’ve we’ve finished DNA finished DNA synthesissynthesis

The cell The cell grows and grows and prepares for prepares for mitosis in G2mitosis in G2

MitosisMitosis

Now we have enough Now we have enough DNA for two daughter DNA for two daughter cellscells

The cells must equally The cells must equally divide the DNA so divide the DNA so each daughter cell each daughter cell gets their own set.gets their own set.

Mitosis: the process of Mitosis: the process of sorting and sorting and dsitributing dsitributing chromosomeschromosomes

ChromosomesChromosomes Each old strand Each old strand

paired with a paired with a new strandnew strand

Called “sister Called “sister chromatids”chromatids”

““sister sister chromatids” chromatids” connected by connected by “centromeres”“centromeres”– Narrow point Narrow point

with proteins with proteins binding them binding them togethertogether

Sister Chromatids

ChromosomesChromosomes Each old strand Each old strand

paired with a paired with a new strandnew strand

Called “sister Called “sister chromatids”chromatids”

““sister sister chromatids” chromatids” connected by connected by “centromeres”“centromeres”– Narrow point Narrow point

with proteins with proteins binding them binding them togethertogether

Sister Chromatids

ChromosomesChromosomes Each old strand Each old strand

paired with a paired with a new strandnew strand

Called “sister Called “sister chromatids”chromatids”

““sister sister chromatids” chromatids” connected by connected by “centromeres”“centromeres”– Narrow point Narrow point

with proteins with proteins binding them binding them togethertogether

Sister Chromatids

MitosisMitosis

Actually a continuous processActually a continuous process Like a film of someone doing a back flipLike a film of someone doing a back flip To make it easier to understand: break it up into To make it easier to understand: break it up into

phasesphases– 1. Interphase1. Interphase– 2. Prophase2. Prophase– 3. Pro-metaphase or Late Prophase3. Pro-metaphase or Late Prophase– 4. Metaphase4. Metaphase– 5. Anaphase5. Anaphase– 6. Telophase6. Telophase– 7. Cytokinesis7. Cytokinesis

InterphaseInterphase

““time between cell divisions”time between cell divisions”– Prepares for mitosisPrepares for mitosis

Chromosomes not visibleChromosomes not visible– Nucleolus easy to spotNucleolus easy to spot

““little nucleus”little nucleus” Round structure in nucleusRound structure in nucleus Makes RNAMakes RNA

Pair of centrioles may be Pair of centrioles may be presentpresent

Important later onImportant later on

Prophase or Early Prophase or Early ProphaseProphase

Chromatin begins to Chromatin begins to condensecondense– Chromosomes become Chromosomes become

visiblevisible Nucleolus disappearsNucleolus disappears Centrioles move to Centrioles move to

opposite endsopposite ends Fibers begin to extend Fibers begin to extend

from centromeresfrom centromeres

Pro-metaphasePro-metaphase

A.k.a. “Late Prophase”A.k.a. “Late Prophase” Not even mentioned in your Not even mentioned in your

bookbook Nuclear membrane Nuclear membrane

dissolvesdissolves Proteins attach to Proteins attach to

centromerescentromeres– Forms Forms kinetochoreskinetochores

This forms the This forms the mitotic mitotic spindle (fibers= spindle (fibers= microtubules)microtubules)

MetaphaseMetaphase

Spindle fibers line Spindle fibers line up chromosomes up chromosomes down middledown middle

Chromosomes line Chromosomes line up on “metaphase up on “metaphase plate”plate”

AnaphaseAnaphase

Paired chromosomes Paired chromosomes separate at centromereseparate at centromere– Protein binding them together Protein binding them together

breaks downbreaks down

Spindle microtubules start Spindle microtubules start pulling chromosomes to pulling chromosomes to opposite ends of cell towards opposite ends of cell towards centriolescentrioles

TelophaseTelophase

Chromosomes arrive Chromosomes arrive at opposite poles of at opposite poles of cellcell

New nuclear New nuclear membranes form membranes form around daughter around daughter nucleinuclei– Keep separated DNA Keep separated DNA

from mixing againfrom mixing again Chromosomes start Chromosomes start

to disperseto disperse– Chromosomes no Chromosomes no

longer visiblelonger visible

CytokinesisCytokinesis

DNA is divided equallyDNA is divided equally Rest of cell divides into two Rest of cell divides into two

identical cellsidentical cells– Can begin during early stagesCan begin during early stages

Animal cells:Animal cells: “actin” constricts “actin” constricts around center of cell til it around center of cell til it pinches it in twopinches it in two

Plant cells:Plant cells: A cell plate is A cell plate is synthesized down the centersynthesized down the center– Like two girls forced to share a Like two girls forced to share a

room build a wall down the room build a wall down the middle of roommiddle of room

– Video1Video1 videovideo22

ENDEND

Mitosis is pauMitosis is pau Parent cell has Parent cell has

finished cell cyclefinished cell cycle Result: 2 Result: 2

daughter cellsdaughter cells– Daughter cells Daughter cells

begin their own begin their own cyclecycle

– Enter G1Enter G1