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Lecture 7

Lecture 7 - Eukaryote - BIOL308.pdf

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BIOL 308
Bruce Wolff

Lecture 7Eukaryote EuThe average size of chromosome is 150 Mbp150 x 103 kbp150x106 bpLength of this DNA would be 150 x 106 bp x 034nm51 x 106 nm51 mmThere are 46 chromosomes in human somatic cell in G1 2n51mm x 462346 mmclose of 25m worth of DNAhuman somatic cellThe average size of eukaryotic cell is anywhere from 10 to 100 microm and DNA is in a nucleus which is even smallerEu cell has to solve even more challenging problem then Pro cell how to pack 25 m2500mm of 2nm thick thread into a ball 10 microm001 mm in diameterEukaryotic ChromaticEukaryotic genomes organized into chromosomesSingle linear DNA molecule gets wrapped up and packed more or less tightly depends on stage in the cell cycle with the help of specific proteins and protein complexesnucleoproteinLong thin strands of nucleoprotein material of eukaryotic chromosome are called chromatinThey get organized into chromatin fibers which further condense to form tightly packed chromosomesBy dark field electron microscopy fiber structure of a chromosome resembles beads on a stringUnipartite chromosomes single linear DNA molecule and its associated proteinschromaticChromatin Organization Beads on a stringThe fundamental unit of organization of the chromatin fiber is nucleosomeEach nucleosome contains a core particle of histone proteins octet which are wrapped by DNAAlso nonhistone proteins are involved and important for chromatin organizationEg Of non histone involved in packagingtopoisomerase Chromatin Organization NucleosomesNucleosomeoctet of histones and wrapped DNAHistones small proteins rich in lysine and arginine basic aaAt normal pH their second amino groups accepts H and becomes NH3Interact with DNA through electrostatic interactionsFive major typesH1 H2A H2B H3 and H4H2A H2B H3 and H4 formacomplex of 8 proteins octetSize of DNA that wraps around octet NOTES FROM LECTURES Page 1
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