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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