Lecture 12 - 6:6 - Biology 172 Lecture 12: Monday June 6,...

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1 Lecture 12: Monday June 6, 2011 Biology 172 Today’s Outline Cell division Mitosis: Interphase Gap phases Events in Mitosis Chromosome movement Control of cell cycle Announcements Tomorrow NO Discussion:
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2 Meiosis There are two types of cell division : meiosis and mitosis. Meiosis produces daughter cells with ½ the amount of hereditary material found in the parent cell. Meiosis is involved only in the production of gametes (eggs and sperm)
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3
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4 Mitosis Mitosis produces daughter cells genetically identical to the parent cell. Accompanied by cytokinesis , the division of the cytoplasm into two daughter cells. Mitosis is the basis of asexual reproduction
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5 Mitosis and the Cell Cycle Chromosomes = DNA wrapped around proteins. Purpose of mitosis: distribute this genetic material to daughter cells during cell division. Before mitosis, each chromosome is duplicated. As mitosis starts, the chromosomes condense from long, thin filaments into compact structures.
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6 Figure 11-3a Unreplicated chromosome Gene 1 Gene 2 The unreplicated chromosome consists of a single, long strand of DNA wrapped around proteins (proteins not shown).
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7 The DNA replicates, resulting in two copies of the same chromosome. Gene 1 Gene 2 Replicated chromosome Copies of same chromosome Gene 1 Gene 2 Condensed replicated chromosome The DNA condenses around its associated proteins, resulting in a compact chromosome that is 10,000 times shorter than its original length. Copies of same chromosome, condensed Centromere
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8 The Cell cycle Chromosomes replicate during S Phase
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9 Discovery of the Gap Phases Interphase also includes two gap phases,. The first gap, called G 1 phase , occurs before S phase. The second gap, G 2 phase , occurs after S phase and before mitosis. During the gap phases, organelles replicate and additional cytoplasm is made in preparation for cell division.
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10 Figure 11-5 Mitosis M S INTERPHASE DIVISION G 2 G 1
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11 Each of the two DNA strands in a replicated chromosome is called a chromatid . Sister chromatids join at the centromere and are exact copies of the same genetic information. G 1 S PHASE AND G 2 Sister chromatids Parent cell: 4 replicated chromosomes Parent cell: 4 unreplicated chromosomes Chromosomes are shown partially condensed to make them visible Chromosomes at Beginning & End of S Phase
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12 OVERVIEW OF MITOSIS
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Lecture 12 - 6:6 - Biology 172 Lecture 12: Monday June 6,...

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