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An abrupt increase in absorbance corresponding to the

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Unformatted text preview: tranded. •  Most have self ­ complementary regions that form hairpin structures. •  Some have well ­defined ter.ary structures. RNA Structure DNA Stability Hea.ng naDve (double ­stranded) DNA is heated above its melDng temperature denatura.on (separates into single strands). •  Two random coil strands have a higher entropy than the double helix. At low T, ΔG is posi0ve and denatura0on of DNA is not favored. As T increases:  ­TΔS > ΔH, making ΔG nega.ve and denatura.on favorable. The midpoint of the curve marks the DNA mel.ng temperature (Tm). DNA Denaturation Na.ve DNA absorbs less light than denatured DNA The maximum difference occurs at a wavelength of 260 nm. This hypochromicity of double stranded DNA can be used to disDnguish between naDve and denatured forms. An abrupt increase in absorbance, corresponding to the sudden melDng of DNA, is seen at Tm. DNA Denaturation Base ­pair composi.on affects DNA mel.ng temperature. Note the rise in DNA melDng temperature as its percent (G + C) increases. Outline: •  Primary Structure of Nucleic Acids •  Secondary and Tertiary Structure of Nucleic Acids –  Plasticity of Secondary and Tertiary DNA Structure –  Stability of Secondary and Tertiary Structure •  DNA Synthesis / Manipulation Chemical DNA Synthesis Molecular & Synthe.c Biology requi...
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