February 28, 2007

February 28, 2007 - February 28, 2007 Eukaryotic...

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Eukaryotic chromosomes Chromatin Long molecule of DNA complexed with proteins Chromosomes After replication consist of 2 chromatids Held together by cohesin Centromere – region where chromatids are held together DNA Packaging The total length of the DNA in a human cell is 2 meters Must be packages in order to fit in the nucleus Chromosomes contain large numbers of proteins called histones All have a positive charge allowing them to interact with the DNA molecules Interactions form bead-like units called nucleosomes ~200 nucleotides complexed around 8 histone proteins A DNA molecule binds with histones forming nucleosomes Nucleosomes pack into a coil that twists forming another coil Coils fold to form loops Loops coil further forming a chromosome Chromosomes Karyotypes Haploid (n) number One complete set of chromosomes Diploid (2n) number 2ce the haploid number Humans N=23 2n=46 Mitosis: Distributing Exact Copies of Genetic Information Interphars DNA replication Cell grows Centrosomes are also doubled Each contains a pair of centrioles During the G2-M transition the centrososmes travel to opposite ends of the cell Form the microtubules that attach to and move the chromosomes during mitosis 5 separate phases Prophase – chromatids become visible; spindle formation Prometaphase – nuclear envelope disappears
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February 28, 2007 - February 28, 2007 Eukaryotic...

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