Lecture 31 - Genetic variation is a good thing Sexual...

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BIOL104-04 Principles of Biology I November 12, 2010 Lecture #31 Chapter 11 Sexual reproduction & meiosis
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Meiosis • A type of cell division • Daughter cells have half as many chromosomes as parent cell • Diploid ! haploid • 2n ! 1n
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Relationship between • Unreplicated chromosome – Single DNA molecule with its associated proteins • Replicated – Two sister chromatids • Tetrad – Homologous chromosomes that are joined together
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Synapsis 2n 2 A 2 B
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Some species reform nuclear membrane - others do not
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Meosis I ! meosis II • Brief interphase • No S phase • No DNA replication
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1n 1A 1B
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Why sex? • Asexual reproduction – Mitosis – Offspring are genetically identical to parents • Sexual reproduction – Offspring are genetically unlike their parents
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Unformatted text preview: Genetic variation is a good thing Sexual reproduction Produces offspring through the fusion of gametes Offspring have chromosomal complements that are Different from each other Different from the parents How does genetic variation happen? Crossing over Exchange of DNA between homologous chromosomes Independent assortment Separation & distribution of homologous chromosomes Random assortment of chromosomes on the metaphase plate Independent assortment Mitosis vs. meosis Mitosis One round of DNA replication One division One cell (2n) ! two cells (2n) Meosis One round of DNA replication Two divisions One cell (2n) ! four cells (1n) Movie In-class activity...
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This note was uploaded on 05/03/2011 for the course BIOL 104 taught by Professor Bray-speth during the Fall '11 term at Saint Louis.

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Lecture 31 - Genetic variation is a good thing Sexual...

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