Chapter 9: Chromosomes and Mitosis
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Transcript of Chapter 9: Chromosomes and Mitosis
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Chapter 9: Chromosomes and Mitosis
p. 198 - 207
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Review of Important Terms:
Gene - segment of DNA that codes for a protein
Chromosome - DNA + proteins, each contains thousands of genes, visible in cell during cell division
Mitosis - the division of the cell nucleus resulting in two daughter cells; consists of 4 phases
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Genes
DNA is organized into genesEach chromosome may contain hundreds - thousands of genesHumans have 35,000 - 40,000 genes that code for proteins
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Chromosomes
located in cell nucleusmade of chromatin - a complex material consisting of proteins and DNA - long, thin threads When a cell is not dividing, chromosomes are present but in an unraveled formDuring division, chromatin fibers condense into chromosome form
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Chromosomes
Every species has a specific number of chromosomes present in the nuclei of body cells
It is not the number of chromosomes that makes the species unique, but the information specified by the genes
Humans have _____ chromosomesMost plants and animals have between ____ and ____ chromosomes
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The Cell Cycle
Cell cycle - sequence of cell growth and divisionDo all cells divide? - Types of cells that do not divide: - nerve - skeletal muscle - red blood cells If cells divide, undergo mitosis
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Cell Cycle
represented by a circlegeneration time - period of one division to the beginning of the next - can vary widely Divison involves 2 main processes: - Mitosis - Cytokinesis
Mitosis.mpg
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Cell Cycle
Interphasemost of the cell's lifeno cell divisionG1 - no DNA synthesis occurs, growth period, longest stageS - DNA replication G2 - shortest of the 3 phases of interphase, completion marks the beginning of mitosis, 2nd phase of growth
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4 phases: 1. Prophase 2. Metaphase 3. Anaphase 4. Telophase
The Stages of Mitosis.mpg
Mitosis
Cell Cycle
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Longest phase: 50-60% of total time in mitosisThe chromosomes become visibleCentrioles - separate and take up positions on opposite sides of the nucleusSpindle begins to form - its job is to help separate the chromosomes Nuclear envelope breaks down
Prophase
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Only lasts a few minutesChromosomes line up across the center of the cellCentromere of each chromosome is attached to the spindle
Metaphase
Centromeres split Sister chromatids separate and become individual chromosomesChromosomes move to opposite ends of the cell
Anaphase
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Final stage of mitosisChromosomes begin to disperse into a tangle of dense materialNuclear envelope reforms around each cluster of chromosomesSpindle breaks apartNucleolus becomes visible in each daughter nucleus
Telophase
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Cell Cycle
Cytokinesisformation of 2 separate daughter cellsdivision of the cytoplasmbegins during telophaseanimals - cleavage furrow developed, gradually deepens and separates the cytoplasm to form 2 cellsplants - cell plate forms
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Attachments
Mitosis.mpg
The Stages of Mitosis.mpg