Week 1 Notes
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This 2 page Class Notes was uploaded by Amanda Notetaker on Thursday January 14, 2016. The Class Notes belongs to 012 at University of Vermont taught by Dr. Hill in Fall 2016. Since its upload, it has received 29 views. For similar materials see Exploring Biology in Biomedical Engineering at University of Vermont.
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Date Created: 01/14/16
CH. 7.4 Meiosis Halves the Nuclear Chromosome Content and Generates Diversity Mitosis (Review) Interphase: visible nucleus, cell functions occur G1 lengthy S DNA replication each chromosome has 2 sister chromatids joined at centromere G2 microtubules synthesized for chromosomes to separate Mitosis: chromosomes separate into two nuclei Prophase Spindle forms Prometaphase Nuclear envelope breaks Metaphase Chromosomes line up in middle Anaphase Chromatids separate Telophase Nuclear envelope reforms Cytokinesis Cell separates into two Source: https://publications.nigms.nih.gov/insidethecell/images/ch4_phases_all.jpg Meiosis (p 142143) Fuctions: reduces chromosome # from diploid cell to haploid gives each haploid set a complete set of chromosomes generates diversity Diploid Cell: 2 sets of chromosomes; one from female parent/one from male parent Haploid Cell: 1 set of chromosomes Meiosis I: (Prophase I, Metaphase I, Anaphase I, Telophase I) 1. Homologous chromosomes combine 2. Homologous chromosome pairs separate, individual chromosomes (2 sister chromatids) stay together 3. Two new nuclei form, each has one member of each homologous pair S: DNA Replication Meiosis II: (Prophase II, Metaphase II, Anaphase II, Telophase II) 1. Sister chromatids in each chromosome separate 2. Creates 4 nonidentical haploid cells (each w/ 1 set of chromosomes) Genetic Diversity Crossing Over: Occurs during Prophase I into Metaphase I Homologous chromosomes pair to form a tetrad between their four chromatids Centromeres repel remaining attached at chiasmata where they share genetic material Results in recombinant chromatids Independent Assortment: Occurs during Anaphase I Depends on which member of homologous pair goes to which daughter cell based on how they line up during Metaphase I The greater the amount of chromosomes, the greater the diversity Errors in Meiosis Nondisjunction: Occurs due to failure to separate during… a) Anaphase I, Homologous pairs don’t separate b) Anaphase II, Sister chromatids don’t separate Results in 2/4 daughter nuclei with extra chromosomes and 2/4 with no chromosomes Aneuploidy: abnormal # of chromosomes; causes miscarriages (Ex: Trisomy 21, down syndrome) Polyploidy: Occurs due to extra round of DNA replication or lack of spindle formation during Meiosis II causes formation of triploid (3n), tetraploid (4n), etc. Triploid cannot undergo normal meiosis due to its odd number of chromosomes would cause one to lack a pair Occurs naturally in some plants (Ex: watermelons become seedless) Translocation: Nonhomologous chromosomes break and join during crossingover in Meiosis I Can be passed on to offspring giving it a great effect on gene expression
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