Mitosis and meiosis Cell Replication

It’s all about the dna...

Genetic storage Humans are a diploid (2n) species; 46 chromosomes Humans gametes are haploid (n); 23 chromosomes

Cell replication: 2 options 1) MITOSIS: division of a nucleus into two genetically identical nuclei (IPMAT) Somatic cells 2) MEIOSIS: division of nucleus that involves two divisions and one duplication of chromosomes; results in haploid (n) gametes with one chromosome from each homogolous pair Gametes (sex cells) CYTOKINESIS: division of a cells cytoplasm into two distinct cells

mitosis 1. Interphase 2. Prophase 3. Metaphase 4. Anaphase 5. Telophase 6. Cytokinesis

Meiosis 1. Interphase 2. Prophase 1 3. Metaphase 1 4. Anaphase 1 5. Telophase 1 6. Cytokinesis 1 7. Prophase 2 8. Metaphase 2 9. Anaphase 2 10. Telophase 2 11. Cytokinesis 2

The Cell Cycle (Mitosis)

Interphase Growth and DNA replication

Prophase Chromosomes condense Nuclear membrane begins to dissolve Spindle fibers attach to the centromeres Centrioles move to opposite poles

Metaphase Chromosomes line up at the equatorial plate Nuclear membrane completely dissolves

Anaphase Centromeres divide and the resulting chromosomes move to opposite poles of the cell Identical chromosomes at each pole

Telophase Chromosomes lengthen again Spindle fibres dissolve Nuclear membrane forms Cytokinesis: Cytoplasm begins to divide A furrow develops pinching of the cell into two parts Resulting in two separate daughter cells

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Mitosis vs. meiosis http://www.pbs.org/wgbh/nova/body/how- cells-divide.html

Interphase DNA has already duplicated Paternal and Maternal Chromosomes

Prophase 1 Chromosomes condense Synapsis Chromosomes condense Homologous chromosomes come together (Tetrad) Crossing over occurs Spindle fibers attach to homologous pairs

Crossing Over

Metaphase 1 Chromosomes line up at the equatorial plate

Anaphase 1 Homologous chromosomes separate to opposite poles

Telophase Nucleus completes its division. Results in two cells that are haploid (x2) Cytoplasm divides during cytokinesis

Prophase 2 Centrioles move to opposite poles Chromosomes become attached to spindle fibres

Metaphase 2 Chromosomes line up at equatorial plate

Anaphase 2 Sister Chromatids of each chromosome separate and move to opposite poles

Telophase 2 Spindle fibres detach Cytoplasm separates (Cytokinesis) Left with four haploid cells

Gametogenesis