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Unformatted text preview: Feb 8 Lecture 7 24-41; Table 23-3 again; 24.42,44,48,46,47; 3.11; 25.1,2,3,4,5,6,9,7; 3.19- Chromatine contains roughly equal numbers of hisotnes H2A, H2B, H3, and H4 and no more than half that number of H1- 2 copies of each of them, so its an octamer- Nucleosome has a lot of moving parts since DNA has to be transcripted- If you chew up with nucleases, the DNA between nuclease, a specific nuclease can chew up the linker DNA and leave the DNA wrapped in histone intact- Amount of DNA left wrapped around the histone core is always 146-147 bp, whether its the nucleosomes from a cow, a tree, or a yeast cell- Extremely conserved structure, no matter what eukaryotic species- Prokaryotes do not have histones- 24.44 o Histone octamer o H1- binds to DNA as it enters and exits the octamer; interacts with neighboring nucleosomes for higher order structure o Left handed wrapping- high energy storage form Equivalent to negative supercoiling Energetically easier to unwind and separation of strand High energy storage form that makes unwinding of watsn base helix is easier o Positive supercoling would not be the case and would make unwinding a lot difficult- 24.48 o How DNA is packed into chromosomes o 1 st order of packing is the Watson crick strans bDNA diameter is 20A o 2 nd order of packing is the nucleosome o 3 rd order of packing is the 30nm fiber...
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- Spring '10