DNA Structure and Function
Heat is often used to separate or denature double stranded DNA into single stranded DNA by breaking the hydrogen bonds between base pairs. Which of the following statements is true?
|A||G-C base pairs would require higher temperatures to break than A-T base pairs.|
|B||A-T base pairs would require higher temperatures to break than G-C base pairs.|
|C||All long DNA chains should denature at the same temperature.|
|D|| DNA-DNA double strands would require higher temperatures to denature that DNA-RNA double strands containing the same sequence.|
Since G-C base pairs contain three hydrogen bonds, whereas A-T base pairs contain only two, the G-C pairing would require more energy, and hence a higher temperature, to disrupt. Extending this idea, long chains of DNA require different temperatures to denature depending on how many G-C pairs they have relative to A-T base pairs. Since there is no difference in the number of hydrogen bonds between a DNA-DNA double strand and a DNA-RNA double strand with the same sequence (A-U base pairs only contain two, just like A-T), there would be no difference in the temperature necessary to denature them.