0 Lecture Notes ECON 437/837: ECONOMIC COST- BENEFIT ANALYSIS Lecture Nine.
Lecture nine
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Transcript of Lecture nine
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Meiosis and Gene Linkage
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PMAT
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Chromosome Number
Diploid
Homologous
Haploid
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Phases of Meiosis
Meiosis
By the end of meiosis II, the diploid cell that entered meiosis has become four haploid cells
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What Happens When It Goes Wrong?
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Meiosis I: Prophase
Tetrad
O Crossing Over
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Meiosis I: Metaphase
Spindle fibers attach to the chromosomes
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Meiosis I: Anaphase
The fibers pull the homologous chromosomes toward opposite ends of the cell
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Meiosis I: Telophase and Cytokinesis
Nuclear membranes form. The cell separates into two cells
These two cells enter Meiosis II
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Meiosis II: Prophase
Unlike the first division, neither cell goes through a round of chromosome replication before entering meiosis II
Each of the cell’s chromosomes has 2 chromatids
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Meiosis II: Metaphase
Chromosomes line up in the center of each cell
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Meiosis II: Anaphase
The paired chromatids separate and move toward opposite ends of the cell
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Meiosis II: Telophase and Cytokinesis
Each cell separates into two cells - meaning four haploid cells all together
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Gamete Formation
In male animals, meiosis produces four haploid sperm cells
However, the cell divisions at the end of meiosis are uneven in females, so that only a single cell receives most of the cytoplasm
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Mitosis vs. Meiosis
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Gene Linkage
It is the chromosomes that assort independently, not the individual genes
Mendel did not discover gene linkage (Morgan did)
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Gene Maps