EXAM 3 - HAPLOID (N) The condition of having one set of...

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HAPLOID ( N ) The condition of having one set of chromosomes per nucleus DIPLOID (2 N ) The condition of having two sets of chromosomes per nucleus In somatic cells of diploid organisms, chromosomes are present in pairs HOMOLOGOUS CHROMOSOMES Members of a chromosome pair that are similar in size, shape, and genetic constitution INTERPHASE Stage of the cell cycle between successive mitotic divisions During interphase cell grows and prepares for next division DNA replicates Interphase is divided into 3 periods first gap phase (G 1 ) synthesis phase (S) second gap phase (G 2 ) MITOSIS Division of the cell nucleus resulting in two daughter nuclei, each with the same number of chromosomes as the parent nucleus CYTOKINESIS Stage of cell division in which the cytoplasm divides to form two daughter cells Prophase Chromatin condenses into chromosomes Nucleolus disappears Nuclear envelope breaks down Mitotic spindle begins to form At the end of prophase, each duplicated chromosome is composed of two sister chromatids SPINDLE Structure consisting mainly of microtubules that provides the framework for chromosome movement during cell division Metaphase Duplicated chromosomes line up along midplane of cell Anaphase Sister chromatids separate and move to opposite poles of the cell Each chromatid is now a separate chromosome Telophase Nuclear envelope forms around each set of chromosomes Nucleoli reappear Chromosomes lengthen and become chromatin Spindle disappears CELL PLATE Structure that forms during cytokinesis in plants, separating two daughter cells produced by mitosis Cytokinesis generally takes place in telophase
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MEIOSIS Process in which a 2 n cell undergoes successive nuclear divisions, potentially producing four n nuclei Leads to formation of spores in plants Meiosis must occur at some time in the life of a sexually reproducing organism if gametes are to be haploid Meiosis consists of two cell divisions Meiosis I Meiosis II Meiosis I Members of each homologous pair of chromosomes separate and are distributed into separate nuclei in two daughter cells Chromosomes were duplicated prior to meiosis I, so each consists of two chromatids Meiosis II Chromatids separate into individual chromosomes and are distributed into different haploid daughter cells Four haploid cells form SYNAPSIS Physical association of homologous chromosomes during prophase I of meiosis Crossing over Exchange of segments of homologous chromosomes Synapsis and crossing over occur during prophase I of meiosis Mitosis Involves a single nuclear division in which the two daughter cells formed are genetically identical to each other and to the original cell Synapsis of homologous chromosomes does not occur during mitosis Meiosis Involves two successive nuclear divisions and forms four haploid cells, each with a
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This note was uploaded on 01/17/2012 for the course NSC 461 taught by Professor Benning during the Fall '11 term at Michigan State University.

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EXAM 3 - HAPLOID (N) The condition of having one set of...

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