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 – 2n Sex cells (gametes) have 23 chromosomes Haploid - n

M 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 Metaphase Prophase Anaphase Cytokinesis 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.. Centrosome Aster Sister chromatids Metaphase Plate Kinetochores Overlapping nonkinetochore microtubules Kinetochores microtubules Chromosomes Microtubules 0.5 µm 1 µm Figure 12.7

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

Mitosis in an Animal Cell

Cleavage furrow Centrioles ANIMAL CELL

Cell plate No centrioles PLANT CELL

Result of Cell Cycle two new daughter cells net gain of only one cell 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