notes 4 - Meiosis I. PLOIDY- number of sets of chromosomes...

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Unformatted text preview: Meiosis I. PLOIDY- number of sets of chromosomes i. Haploid- 1 set, 1n ii. diploid- 2 sets, 2n iii. tetraploid- 4 sets, 4n iv. anueploid- change in the # of a single chromosome (eg. Downs syndrome) II. Homologous Chromosomes: i. Chromosomes containing the same genes ii. Chromosomes that carry genes for the same traits iii. same length iv. centromere in the same location. These chromosomes are called homologues, or a homologous pair. III. MEIOSIS: A. Meiosis results in haploid nuclei being formed from diploid nuclei. i. Often called a " reductional division " ii. Typically during sexual reproduction, in a diploid organism two haploid cells fuse restoring the diploid condition. iii. In an organism each of the haploid cells must contain one chromosome from each chromosome pair, otherwise the resulting cell would be missing some genes. iv. produces non-identical daughter cells with the # of parental cells chromosomes B. Meiosis also consists of 2 separate divisions i. Meiosis I- separates homologous chromosomes ii. Meiosis II- separates sister chromatids C. Phases of Meiosis: 1. Prophase I i. Synapsis- homologous chromosomes together, cross over at chiasmata ii. tetrad- structure of two homologous chromosomes together, four chromatids iii. Crossing-over- result of synapsis, 2. Metaphase I i. homologous pairs line up on metaphase plate 3. Anaphase I i. homologous pairs orient towards cell poles 4. Telophase I/ Cytokinesis i. Segregation: Homologues separate into different cells ii. Independent Assortment: Different pairs assort independently iii. Interkinesis- resting stage between meiosis I and meiosis II, separate from interphase because no replication occurs (like in S phase) 6. Prophase II i. almost exact same concept as prophase in mitosis, separating of sister chromatids of a single, replicated chromosome 7. Rest of Meiosis II identical to Mitosis phases IV. Alternation of Generations A. organisms with multicellular haploid and diploid stages Mendelian Genetics often called Diploid Genetics, or Classical Genetics Inheritance of units corresponds to inheritance of chromosomes in meiosis I a. Heredity : Transmission of characteristics from parent to offspring b. Role of the parent: produce gametes I. Reproduction i. asexual- primarily through mitosis, identical offspring ii. sexual- through meiosis, offspring different than parents and each other iii. what is the role of the parent?...
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This note was uploaded on 02/14/2011 for the course BIOL 1201 taught by Professor Wishtichusen during the Spring '07 term at LSU.

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notes 4 - Meiosis I. PLOIDY- number of sets of chromosomes...

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