M phase

DNA at different phases

chromatinchromosome

histone

nucleosome

DNA at different phasesDNA at different phases

• Chromatin- DNA + protein- before cell division (M phase)

• Chromosome- condensed chromatin during cell division

• Sister Chromatid- each individual double helix

FYI..FYI..

• Body cells (autosomes/somatic cells) have 46 chromosomes or 23 pairs – Diploid – 2n

• Sex cells (gametes) have 23 chromosomes– Haploid - n

M phaseM phase

• Mitosis (nuclear division)

• Cytokinesis (cytoplasmic division)

Mitosis

• Nuclear division

• Cell growth stops

• Produces 2 similar daughter cells (2n)

• Asexual reproduction

• 1-2 hrs only

• Metaphase Checkpoint

Stages of Mitosis

Prophase Metaphase Anaphase

TelophaseCytokinesis

Prophase

• Chromatin thickens into chromosomes

• Nuclear membrane and nucleolus disintegrates

• Mitotic spindle forms

• Centrosome pairs move to opposite ends

Prophase

Prophase

Metaphase

•Chromosomes at metaphase plate

•Centrosomes at opposite poles

•Kinetochores attached to microtubules

Secrets on how chromosomes Secrets on how chromosomes move..move..

Secrets..

Spindlepole

Kinetochore

microtubule

Anaphase

•Centromeres divide

•Chromatids now chromosomes

•Kinetochore microtubules shorten - Chromosomes separate and

move

•Nonkinetochore microtubules lengthen

•End: chromosomes at 2 poles

Motor protein

Telophase

• Chromosomes arrive at opposite poles

• Spindle fibers disintegrate

• Nuclear membrane reforms & Nucleolus reappears

• Chromatin fibers become less tightly coiled

Cytokinesis

•Cytoplasm divides

•Animals: cleavage furrow divides cytoplasm

•Plant cells: cell plate

•Two daughter cells

• Cell pinches inward

Daughter cells

1 µmVesiclesforming cell plate

Wall of patent cell Cell plate New cell wall

Cell Plate FormationCell Plate Formation

Mitosis in an Animal Cell

•Cleavage furrow

•Centrioles

ANIMAL CELL

•Cell plate

•Nocentrioles

PLANT CELL

Result of Cell CycleResult of Cell Cycle

• two new daughter cells– identical to the parent cell in chromosome

number and chromosome type

• net gain of only one cell • two new daughter cells will enter

interphase and the cycle will continue… 

Cell CycleCell Cycle