BS110 Meiosis and Mitosis

BS110 Meiosis and Mitosis - The Chromosomal Basis of...

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The Chromosomal Basis of Inheritance: Meiosis and Mitosis 11 Feb 2008 BS 110
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Why study meiosis? Meiosis is nuclear division in eukaryotic sex cells Responsible for much variability among individuals Determines who gets what parental features Crucial to study of inheritance (genetics) Underlies paradox of sex Why do so many organisms undertake the costly process of sex? Meiotic mistakes result in spontaneous abortion, abnormalities
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Sexual reproduction Egg and sperm (gametes or sex cells) whose genetic contents determined by meiosis unite Fertilization Forms a new individual (zygote) Eventually an embryo, then adult Employed in a minority of organisms Some never Some rarely But sex drives evolution of many organisms Gametes defined by relative sizes: male small, female large
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Meiosis vs. Mitosis Mitosis is nuclear division that results in two daughter nuclei genetically “identical” to parent No recombination or crossing over Mutations not passed to offspring in sexual species Most asexual reproduction by mitosis Meiosis is nuclear division in which parent cell with two copies of each chromosome produces 4 non-identical daughter cells with one copy of each Recombination and crossing over causes variation Mutations in sex cells may be passed to offspring Mostly occurs in sexually reproducing organisms Neither occurs in prokaryotes
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Chromosome: a single long molecule of DNA Many genes plus any associated proteins Each species has characteristic number of chromosomes in each somatic (body) cell 46 in humans; 48 in chimpanzees Chromosomes paired in somatic cells Homologous chromosomes or homologs
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This note was uploaded on 03/19/2008 for the course BS 110 taught by Professor S.lawrence during the Spring '07 term at Michigan State University.

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BS110 Meiosis and Mitosis - The Chromosomal Basis of...

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