Week 3, Lecture 2, Mitosis

Week 3, Lecture 2, Mitosis - 1 B I O L O G Y 0 2 3...

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Unformatted text preview: 1 B I O L O G Y 0 2 3 19-Sep-09 Gardiner 1 Cell Cycle and Mitosis B I O L O G Y 0 2 3 19-Sep-09 Gardiner 2 Why do cells divide? Genetically Programmed Surface to Volume Ratio External Stimulus B I O L O G Y 0 2 3 19-Sep-09 Gardiner 3 Mitosis • Mitosis – the equal division of one nucleus into two genetically identical nuclei • Mitosis has to do with nuclear division not cell division B I O L O G Y 0 2 3 19-Sep-09 Gardiner 4 M (mitosis) • Chromosomes have two chromatids • Chromosomes condense (prophase) • Chromosomes align at middle of cell (metaphase) • Chromatids separate (anaphase) •-amount of DNA in chromosomes ½ •-ploidy number remains the same • Cell divides (telophase, cytokinesis) B I O L O G Y 0 2 3 19-Sep-09 Gardiner 5 Ploidy • The number of complete chromosome sets in a nucleus • Diploid organisms ( 2n ) are those with two sets –i.e. humans, animals and many plants. • Haploid organisms / cells ( n ) have only one set of chromosomes. • Polyploid organisms have more than 2 sets of chromosomes B I O L O G Y 0 2 3 19-Sep-09 Gardiner 6 2 B I O L O G Y 0 2 3 Each chromosome is two chromatids per chromosome Each chromatid is a DNA double helix B I O L O G Y 0 2 3 Each human body cell has 46 or 23 pairs of these chromosomes during late prophase and metaphase B I O L O G Y 0 2 3 19-Sep-09 Gardiner 9 Cell division in Eukaryotic cells has two components Mitosis = division of the nucleus Cytokinesis = division of the cytoplasm Fig. 9.4 B I O L O G Y 0 2 3 Interphase B I O L O G Y 0 2 3 19-Sep-09 Gardiner 12 Interphase Occurs before stages of mitosis Genetic material is called Chromatin DNA replication occurs during this phase 3 Interphase •Nucleus well defined •Nucleoli present •Centrosomes replicated (replicated centrioles in animal cells only) •Microtubules extend from centrosomes (called aster [star]) •Chromosomes have duplicated but not condensed...
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This note was uploaded on 04/18/2010 for the course BIOLOGY 1223 taught by Professor Gardiner/lajoie during the Spring '09 term at UWO.

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Week 3, Lecture 2, Mitosis - 1 B I O L O G Y 0 2 3...

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