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 “Beads on a string” Nucleosome Tight helical fiber Supercoil Sister chromatids 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 other Chromosome duplication Sister chromatids Chromosome distribution to daughter cells Attached by a centromere

Mitosis Mitosis and Cytokinesis –Is the division (separation)of the chromosomes Interphase Centrosomes (with centriole pairs) Nucleolus Nuclear envelope Plasma membrane Chromatin Mitosis consists of five distinct phases –Prophase –Metaphase –Anaphase –Telophase –Cytokinesis

Early mitotic spindle CentrosomeCentromere Chromosome, consisting of two sister chromatids Spindle microtubules Fragments of nuclear envelope Metaphase Spindle Prophase PROPHASE 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 Daughter chromosomes Cleavage furrow Nuclear envelope forming Nucleolus forming

CYTOKINESIS different in plant and animal cells –Typically occurs during telophase –Is the division of the cytoplasm Cleavage furrow Cleavage furrow Contracting ring of microfilaments Daughter cells (a) Animal cell cytokinesis

Wall of parent cell Cell plate forming Daughter nucleus Cell wall Vesicles containing cell wall material Cell plate New cell wall Daughter cells (b) Plant cell cytokinesis

MITOSIS & the CELL CYCLE vimeo