M phase DNA at different phases histone nucleosome

M phase

DNA at different phases histone nucleosome chromatin chromosome

DNA at different phases • Chromatin - DNA + protein - before cell division (M phase) • Chromosome - condensed chromatin during cell division • Sister Chromatid - each individual double helix

FYI. . • Body cells (autosomes/somatic cells) have 46 chromosomes or 23 pairs – Diploid – 2 n • Sex cells (gametes) have 23 chromosomes – Haploid - n

M phase • Mitosis (nuclear division) • Cytokinesis (cytoplasmic division)

Mitosis • Nuclear division • Asexual reproduction • Cell growth stops • 1 -2 hrs only • Produces 2 similar daughter cells (2 n) • Metaphase Checkpoint

Stages of Mitosis Prophase Cytokinesis Metaphase Anaphase Telophase

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 move. .

Secrets. . Kinetochore Spindle pole

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

Cell Plate Formation Vesicles forming cell plate Wall of patent cell Cell plate 1 µm New cell wall Daughter cells

Mitosis in an Animal Cell

• Cleavage furrow • Centrioles ANIMAL CELL

• Cell plate • No centrioles PLANT CELL

Result 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 Cycle