MITOSIS & CYTOKINESIS

A genome

– Is the complete set of an organism’s genes

– Is located mainly on DNA in the cell’s nucleus

• NAMES FOR DNA in different parts of the Cell Cycle

• Chromatin - DNA-protein complex

• Chromosome – condensed chromatin

• Chromatids –duplicated chromosomes

Eukaryotic Chromosomes

– Are made of

chromatin, a

combination of

DNA and protein

molecules

– Are not visible in

a cell until cell

division

• The DNA in a cell is

packed into an elaborate,

multilevel system of

coiling and folding

DNA double helix

Histones

“Beadson astring”

Nucleosome

Tight helical fiberSupercoil

Sisterchromatids

Centromere

Histones are a family of small,

positively charged proteins that coli

the DNA into the nucleus

Nucleosome = DNA + histones

In a repeating pattern

DNA DUPLICATION (INTERPHASE)

Before a cell divides DNA COPIES

DNA uncoils (G1 phase)

DNA duplicates (S phase)

DNA separates into smaller attached units called

sister chromatids (G2 phase)

Occurs in INTERPHASE

• When the cell divides,

the sister chromatids

separate from each

otherChromosomeduplication

Sisterchromatids

Chromosomedistribution

todaughter

cells

Attached by a centromere

• Mitosis

Mitosis and Cytokinesis

– Is the division

(separation)of the

chromosomes

Interphase

Centrosomes (with centriole pairs)

NucleolusNuclearenvelope

Plasmamembrane

Chromatin

• Mitosis consists of five distinct phases

–Prophase

–Metaphase

–Anaphase

–Telophase

–Cytokinesis

Earlymitoticspindle

Centrosome Centromere

Chromosome, consistingof two sister chromatids

Spindlemicrotubules

Fragments ofnuclear envelope

Metaphase

Spindle

ProphasePROPHASE

• Chromatin

condenses

• Nuclear

membrane

breaks down

• Nucleolus

disappears

• Chromatids

become

visible

• Microtubules,

spindle fibers

centrioles

form

METAPHASE

• Spindle

fibers attach

to the

centromere

• Chromatids

align in the

center

ANAPHASE

Sister chromatids

separate

Spindle fibers shorten

TELOPHASE

Identical chromosomes at the end

in each cell

Nuclear membrane starts forming

Chromosomes begin uncoiling

Anaphase Telophase and Cytokinesis

Daughterchromosomes

Cleavagefurrow

Nuclearenvelopeforming

Nucleolusforming

• CYTOKINESIS different in plant and

animal cells

ANIMAL: Cleavage Furrow

PLANT: cell plate divides then cell wall

forms

– Typically starts during telophase

– Is the division of the cytoplasm

Cleavagefurrow

Cleavage furrow Contracting ring ofmicrofilaments

Daughter cells

(a) Animal cell cytokinesis

Wall of parent cell

Cell plateforming

Daughternucleus

Cell wall

Vesicles containingcell wall material

Cell plate

New cell wall

Daughter cells(b) Plant cell cytokinesis

MITOSIS & the CELL CYCLE vimeo