BIOL 261 Study Guide - Midterm Guide: Eukaryotic Dna Replication, Phosphodiester Bond, Adna, Washington
6 Jan 2015
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Nitrogenous bases purines: adenine & guanine (cid:0) double ring pyrimidines: cytosine & thymine (cid:0) single ring. Chargaff"s rule: amount a = t, amount g = c, a&t (cid:0) g & c (cid:0) organism specific. Dna strand/helix: has polarity/directionality 5"-3", backbone sugar+ phosphate, antiparallel strands. Dna stability: h-bonds btwn strands (cid:0) weak bonds stable w/multiple bonds btwn strands (2 a&t, 3. *dna denatured by high temps/low salt concentrations & even though 2 strands unfold (h- bonds broken), each strand remains intact. Major&minor grooves differ in protein binding sites. Dna supercoiling produces tension in dna structure necessary for most biological functions, like replication, in bacteria & euks twist = # helical turns writhe = # coil overlaps. Dna replication 3 proposed models: conservative, semiconservative, dispersive. Meselson & stahl exp: grow e. coli in presence 15n (heavy isotope) Grow e. coli in 14n (light) for 1 cycle.
