BIOL10002 Lecture Notes - Lecture 8: Sister Chromatids, Nuclear Membrane, Prometaphase
Lecture 8
Cell Division, Mitosis & Meiosis
Bacterial Division
- Binary fission
- FtsZ protein (filament temperature sensitive) pinches cell in half
- Homologue of eukaryotic cytoskeletal protein tubulin (flagella, mitosis)
- Involved in division of chloroplasts and mitochondria (endosymbiotic bacteria)
Cell Cycle
G1: Metabolic changes prepare the cell for division. At a certain point the cell is committed to
division and moves into the S phase.
S: DNA synthesis replicates the genetic material. Each chromosome now
consists of two sister chromatids.
G2: Metabolic changes assemble the cytoplasmic materials necessary for mitosis
and cytokinesis.
M: A nuclear division (mitosis) followed by a cell division (cytokinesis).
Mitosis
Interphase: Nucleus replicates DNA, centrosomes and proteins
Prophase: DNA condenses into x shape, centrosomes migrate to poles of cell
Prometaphase: Nuclear envelope breaks down, kinetochores connect to
centromeres
Metaphase: DNA lines up on equatorial plane
Anaphase: Phosphorylation of protein, centromere breaks and DNA is dragged to
each mitotic centre (forms a V shape) by shortening spindle fibres
Telophase: Spindle fibres let go, new nuclear envelope forms, cytokinesis pinching
done by actin, elongation of chromatin. Results in 2 diploid daughter cells.
Meiosis
This only occurs in Eukaryotes.
Meiosis I – reduces chromosome number from diploid to haploid
Prophase I: Chromosomes condense and genetic exchange occurs (chiasma)
Prometaphase I: Nuclear envelope disassembles
Metaphase I: Chromosomes move to centre and line up along equatorial plane
Anaphase I: Homologues separate to opposite ends of the cell
Telophase I: Chromosomes gather at poles of cells and cell divides. Each
chromosome has 2 sister chromatids.
~ interkinesis ~
Meiosis II – very similar to mitosis, except there is also genetic differences
Prophase II: (note: starting cells are haploid) Chromosomes condense into x shape
Prometaphase II: Nuclear envelope disassembles
Metaphase II: Chromosomes line up at metaphase plate
Anaphase II: Sister chromatids separate to opposite ends of the cell
Telophase II: 2nd cell division resulting in 4 genetically different haploid daughter cells (gametes).
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Document Summary
Ftsz protein (filament temperature sensitive) pinches cell in half. Homologue of eukaryotic cytoskeletal protein tubulin (flagella, mitosis) Involved in division of chloroplasts and mitochondria (endosymbiotic bacteria) At a certain point the cell is committed to division and moves into the s phase. Each chromosome now consists of two sister chromatids. G2: metabolic changes assemble the cytoplasmic materials necessary for mitosis and cytokinesis. M: a nuclear division (mitosis) followed by a cell division (cytokinesis). Prophase: dna condenses into x shape, centrosomes migrate to poles of cell. Prometaphase: nuclear envelope breaks down, kinetochores connect to centromeres. Anaphase: phosphorylation of protein, centromere breaks and dna is dragged to each mitotic centre (forms a v shape) by shortening spindle fibres. Telophase: spindle fibres let go, new nuclear envelope forms, cytokinesis pinching done by actin, elongation of chromatin. Meiosis i reduces chromosome number from diploid to haploid. Prophase i: chromosomes condense and genetic exchange occurs (chiasma)
