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Unformatted text preview: 1 April 22, 2008 April 22, 2008 Biology 113, Lecture 8 Biology 113, Lecture 8 Concepts: 12.1 and 12.2 Part 1 Part 1 - Overview Overview The key roles of cell division The mitotic cell cycle The Cell Cycle - Chapter 12 Dividing E. coli cells Cell division Cell division Division of unicellular organisms reproduces the entire organism, increasing the total population Division in multicellular organisms, Enables its development from a single fertilized egg or zygote (through the miracle of cellular differentiation) Functions to repair and renew cells that die Cell division requires the duplication and distribution of identical genetic material (DNA) to the daughter cells The human chromosome complement The human chromosome complement Chromosomes are composed of DNA with associated proteins (histones) - chromatin Somatic cells have 46 chromosomes (2 sets of 23, one set from each parent) Gametes (sperm and eggs) have 1 set of 23. The genome is the total complement of DNA Human karyotype (an ordered display of the pairs of chromosomes from a cell) Figure 12.4 Before duplication each chromosome has a single DNA molecule Once duplicated, a chromosome consists of 2 sister chromatids (copy of DNA molecule) connected at the centromere Mechanical processes separate the chromatids into daughter cells. Each is now a chromosome. The cell cycle The cell cycle (Gap1) (Gap2) Figure 12.5 Mitosis and cytokinesis (M phase) are a small part of the overall cell cycle Interphase accounts for most of the cell cycle (~90%) (non- dividing cells are in interphase) Typical human cell cycle may take 24 hours (M phase, ~1 hour Most cells exit the cell cycle (G Most cells exit the cell cycle (G ) (G ) 2 Interphase Interphase : cell growth : cell growth and and DNA replication DNA replication G 1 phase: (first gap) Cell growth S phase: DNA synthesis (chromosome replication) G 2 phase: (second gap) Cell growth and preparation for cell division Note: Interphase is not a resting stage. Cells are metabolically active and many events critical to the cell cycle take place during interphase Cell division Cell division - integrated processes integrated processes Mitosis: division of the nucleus Stages (really a continuum but divided for descriptive convenience) Prophase Prometaphase Metaphase Anaphase Telophase Cytokinesis: division of the cytoplasm G 2 of of interphase interphase nucleolus present...
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This note was uploaded on 04/29/2008 for the course BIO 113 taught by Professor Swenson during the Spring '08 term at Ohio State.
- Spring '08
- Cell Cycle