BCHM 4116 1st Edition Lecture 4 Outline of Last Lecture I Structural transitions of DNA II Implication for nucleic acid hybridization Outline of Current Lecture I Tertiary Structure in DNA II L T W III Supercoil IV DNA V The secondary and tertiary structures of RNAs Current Lecture I Tertiary Structure in DNA a Spiral around an imaginary toroid b DNA interwinds and wraps about itself c Long linear DNA loops ends restrained i DNA attached to nuclearmatrix ii 1 end fixed so forms supercoils iii Make sure as you transcribe release stress tension iv Enzyme topoisomerase I dues this by cutting 1 line to release pressure and seals back when finished v Enzyme topoisomerase II does this by cutting both strands And will seal when done vi DNA gyrase is a topoisomerase that introduces negative supercoil into DNA II L T W a L linking number i Number of times two strands are intertwined b T twist i Number of helical turns c W writhe i Number of supercoils III Supercoil a Negative supercoil more relaxed between the two twisted strand b Positive supercoil more tight These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute IV DNA a DNA is negatively charged b Histone is positively charged i This is why DNA wraps around histone c histone code V The secondary and tertiary structures of RNAs a Pseudouridine N glycosidic which would have linked base to sugar via N but in this case base is linked to sugar via C
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