Key Topics Week 5: Anthony Vu Lecture #14: Meiosis 10/25/10 •Meiosis: Mitotic Division that reduces chromosome number. - Meiosis I seperates homolgous chromosomes- Homologous chromosomes are paired chromosomes that are able to cross over and synapse. •Steps of Meiosis I1) Prophase I: Sister Chromatids pair with another set of sister chromatids forming homologous pairs, Crossing over takes place between non-sister chromatids. 2) Metaphase I: Homologous Chromosomes align on metaphase plate 3) Anaphase I: Homolgous Chromosomes are pulled towards opposing poles yielding sister chromatids. 4) Telophase + Cytokinesis: Nuclear envelope may reform and DNA may Decondense but DNA is not replicated again transition to Meiosis II. 5) Meiosis II: Separates Sister Chromatids - Very similar to Mitosis but the end result is 4 cells that are genetically different from original parents. - When non-disjunction occurs; a pair of sister chromatids may not seperate properly leading to uneven distribution leading to disease such as trisomy 21; Down's syndrome.
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