Javad Jamshidi Fasa University of Medical Sciences, November 2015 Genes, Genomes and Chromatin Organization

2 Gene is a Unit of DNA that contains the information to specify synthesis of a single polypeptide chain or functional RNA A genome is an organism's complete set of DNA, including all of its genes.

3 Genome is differently organized in different species

4 Yeasts, 12 Mb Fruit flies, 180 Mb Chickens, 1300 Mb Humans 3300 Mb Much of the DNA in certain organisms does not encode RNA or have any apparent regulatory function The density of genes varies greatly in different regions of human chromosomal DNA

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6 The DNA-protein complex which exist in eukaryotic cells, is highly conserved in all eukaryotes. Both histones and non-histones are involved in physical structure of the chromosome Histones are abundant, small proteins. The five main types are H1, H2A, H2B, H3 and H4, highly conserved, positively charged The DNA is organized inside the nucleus from linear double strand to chromosomes

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8 Consists of a protein core with DNA wound around its surface The core is an octamer containing two copies each of histones H2A, H2B, H3, and H4 Nucleosomes from all eukaryotes contain 147 base pairs of DNA wrapped one and two- thirds turns around the protein core The length of the linker DNA is variable among species, and even between different cells of one organism, ranging from about 10 to 90 base pairs

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15 Histone tails are subject to multiple post-translational modification Acetylation, methylation, phosphorylation, and ubiquitination Influences chromatin function by creating or removing binding sites for chromatin-associated proteins dependent on the specific combinations of these modifications present